Know Your Fish
Cooking Skills: Fish and Shellfish 1
Chapter 1 · Know Your Fish
Skill goal
Buy fresh fish, store it safely, prepare it and tell when it is cooked.
Shopping list for this chapter
The basics
Fish splits into a few groups with different tastes and textures. White fish (cod, haddock, pollock, hake) is mild, lean and flaky. Oily fish (salmon, mackerel, sardines, trout) has richer, stronger flesh full of healthy oils and is harder to overcook. Flat fish (plaice, sole, halibut) is thin, delicate and quick. Shellfish is covered in chapter 6. Fish is lean and has very little connective tissue, which is why it cooks in minutes and dries out as fast.
Fresh fish should smell of the sea, not of ammonia or "fishiness". Look for bright, clear eyes, shiny skin, firm flesh that springs back when pressed and red gills; fillets should be glossy and moist, not dull, gaping or brown at the edges. Frozen fish is often frozen within hours of being caught, so it can be fresher than fish on ice that has travelled for days. Look for the MSC (wild) or ASC (farmed) label, and ask at the counter about where the fish is from. Knife work for fish is in Cooking Skills: Knife Skills 1.
The method
- Buy it last and cook it soon. Take it home in a cool bag, and cook fresh fish the same day or the next.
- Store it at the bottom of the fridge (0 to 4°C), loosely wrapped on a plate, for no more than a day or two.
- Check for pin bones by running a finger down the middle of the fillet, and pull out any with clean tweezers.
- Pat it dry with kitchen paper before cooking, because wet fish steams instead of browning.
- Cook until just opaque, then rest it for a minute; it keeps cooking off the heat.
| Group | Examples | Flavour and texture | Cook it by |
|---|---|---|---|
| White fish | Cod, haddock, pollock, hake | Mild, lean, large flakes | Frying, baking, poaching, battering |
| Oily fish | Salmon, mackerel, sardines | Rich, firm, strong | Frying, grilling, roasting, smoking |
| Flat fish | Plaice, sole, halibut | Delicate, thin | Quick frying, grilling |
| Smoked fish | Haddock, mackerel, salmon | Salty, smoky | Poaching, flaking, pâté |
Raw fish, bones, allergens and smell
Raw fish: keep raw fish on its own board and plate, away from food that won't be cooked. Wash your hands, boards and knives in hot soapy water afterwards, and store raw fish on a plate on the bottom shelf of the fridge so it can't drip onto other food.Bones: even fillets can hide thin pin bones. Run a clean finger along the fillet and pull any bones out with tweezers, and warn children and anyone you serve. Whole sardines and mackerel have fine bones that are best taken out.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Smell and cooking fish: fish smells strongest when it is old, so buy it fresh and cook it the day you buy it. Use the extractor fan and open a window, wrap trimmings tightly before binning them, and wash pans straight away in hot, soapy water.
Try it
Level 1 · Start here
A salt-and-lemon seared fillet
The simplest way to cook a fillet and to taste fish as it is. Pat it very dry, season just before it goes in the pan, and leave it alone. Lemon at the end brightens everything. Pan-frying is covered in more detail in chapter 2.
Ingredients (2 portions)
- 2 skin-on white fish fillets (about 150 g each), pin-boned
- ½ tsp flaked sea salt
- 1 tbsp rapeseed or sunflower oil
- 10 g butter
- 1 lemon, cut in wedges
- Pat the fish very dry with kitchen paper and season both sides with salt. Heat the oil in a non-stick pan over a medium-high heat until it shimmers.
- Lay the fish skin side down, pressing gently with a fish slice for 10 seconds, and cook 3 to 4 minutes without moving it, until the flesh has turned opaque two-thirds of the way up.
- Turn, add the butter and cook for 1 to 2 minutes more. Serve at once with lemon wedges.
Hot pan, raw fish and allergens
Hot pan and hot oil: frying fish uses a hot pan and spitting oil. Dry the fish well, lay it down away from you, use a splash guard if you have one, keep the handle turned in and keep children well back.Raw fish: keep raw fish on its own board and plate, away from food that won't be cooked. Wash your hands, boards and knives in hot soapy water afterwards, and store raw fish on a plate on the bottom shelf of the fridge so it can't drip onto other food.
Is it cooked?: fish is done when the flesh turns opaque (no longer glassy) and flakes easily with a fork. A probe thermometer reads about 63°C in the thickest part (general guidance). Take it off the heat a minute early, because it keeps cooking as it rests.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Level 1 · Baked
Baked fish fingers
Home-made fish fingers are crisper and tastier than shop-bought, and baking is easier and safer than frying. Preheat the tray so the underside crisps. Serve with peas, chips or bread and tartare sauce (mayonnaise is in Cooking Skills: Eggs 2, chapter 7).
Ingredients (4 portions)
- 400 g skinless, boneless white fish fillets
- 50 g plain flour
- 1 egg, beaten
- 100 g panko or fresh white breadcrumbs
- 2 tbsp rapeseed or sunflower oil
- ½ tsp flaked sea salt
- Heat the oven to 220°C (200°C fan, gas 7) with a baking tray inside. Cut the fish into 8 fingers about 2 cm thick and 8 cm long and pat dry.
- Roll each finger in flour (shake off the extra), then the egg, then the breadcrumbs mixed with the oil and salt, pressing the crumbs on.
- Lay on the hot tray and bake for 12 to 15 minutes, turning once, until golden and the fish is cooked through.
Raw fish, hot oven and allergens
Raw fish: keep raw fish on its own board and plate, away from food that won't be cooked. Wash your hands, boards and knives in hot soapy water afterwards, and store raw fish on a plate on the bottom shelf of the fridge so it can't drip onto other food.Hot oven and hot trays: ovens, trays and tins are hot enough to burn badly. Use dry oven gloves (a damp cloth conducts heat), pull the shelf out a little before lifting a tray, put hot things on a heatproof surface and keep children away from the oven door.
Is it cooked?: fish is done when the flesh turns opaque (no longer glassy) and flakes easily with a fork. A probe thermometer reads about 63°C in the thickest part (general guidance). Take it off the heat a minute early, because it keeps cooking as it rests.
Allergens: contains fish, gluten and egg.
Level 2 · No cooking
Sardines on toast
Tinned sardines in olive oil are cheap, rich in oils and ready to eat. The skill is balance: oily fish needs something sharp and fresh. Mash them roughly with lemon, pile on toast and add tomato and parsley.
Ingredients (2 portions)
- 1 tin of sardines in olive oil (about 120 g), drained
- 2 thick slices of bread, toasted
- 1 tbsp lemon juice
- 1 tomato, sliced
- 1 tbsp chopped parsley
- 1 pinch black pepper
- Mash the sardines roughly with the lemon juice and pepper, leaving some texture. Remove any large bones if you prefer.
- Toast the bread, top with tomato slices and pile on the sardines.
- Scatter with parsley and eat straight away.
Bones and allergens
Bones: even fillets can hide thin pin bones. Run a clean finger along the fillet and pull any bones out with tweezers, and warn children and anyone you serve. Whole sardines and mackerel have fine bones that are best taken out.Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Smoked and oily fish for some people: pregnant women, young children, the elderly and people with weak immune systems are advised to limit oily fish and shark, swordfish and marlin, and to avoid raw or lightly cooked shellfish and, for some, cold-smoked fish. This is general guidance, not medical advice: check current health guidance if it applies to you.
Level 3 · Smoked
Smoked mackerel pâté
Smoked mackerel is already cooked, so this needs no heat. Remove the skin and any bones, then blend with cream cheese and lemon. Serve cold on toast or with crackers and cucumber.
Ingredients (4 portions)
- 200 g smoked mackerel fillets, skin and bones removed
- 100 g full-fat cream cheese
- 2 tbsp crème fraîche
- 1 tbsp lemon juice
- 1 tsp creamed horseradish (optional)
- 1 pinch black pepper
- Flake the mackerel into a bowl and check carefully for bones.
- Mash with the cream cheese, crème fraîche, lemon juice, horseradish and pepper, or pulse in a food processor, until almost smooth.
- Taste (smoked fish is salty, so it may need no salt), spoon into a dish, and chill for 1 hour. Eat within 2 days.
Smoked fish, bones and allergens
Smoked and oily fish for some people: pregnant women, young children, the elderly and people with weak immune systems are advised to limit oily fish and shark, swordfish and marlin, and to avoid raw or lightly cooked shellfish and, for some, cold-smoked fish. This is general guidance, not medical advice: check current health guidance if it applies to you.Bones: even fillets can hide thin pin bones. Run a clean finger along the fillet and pull any bones out with tweezers, and warn children and anyone you serve. Whole sardines and mackerel have fine bones that are best taken out.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Leftover fish: cool cooked fish quickly, refrigerate it within 1 to 2 hours, and eat it within about 1 day (2 at most). Reheat only once, until steaming hot all the way through. Do not refreeze fish that was frozen and thawed unless you cook it first.
Experiments
Experiment
Fresh against frozen
Quality.
- Cook a fresh fillet and a defrosted frozen fillet of the same fish exactly the same way.
Look for: Good frozen fish is often almost the same, sometimes better than fish left on ice for days. Defrost in the fridge overnight and pat very dry.
Experiment
Salting 15 minutes first
Firmness.
- Salt one fillet and leave it for 15 minutes before cooking; salt another just before cooking.
Look for: The early-salted fillet is firmer and seasoned deeper, with a little less water. Dry it well afterwards.
Experiment
Skin on or off
Crispness and moisture.
- Pan-fry a skin-on fillet and a skinless one, skin side down first.
Look for: The skin protects the flesh and crisps into a delicious layer; the skinless one cooks faster and can stick.
Experiment
Checking by sight and thermometer
Doneness.
- Cook a thick fillet and check it at 3, 4 and 5 minutes with a fork and a probe thermometer.
Look for: Opaque and flaking arrives at about 60 to 63°C. Past 70°C it is dry. You will learn the look.
Tasting notes
| What I tried | Method or amount | What I saw | What I thought | Will I do it again? |
|---|---|---|---|---|
| Seared fillet | ||||
| Baked fish fingers | ||||
| Sardines on toast | ||||
| Smoked mackerel pâté | ||||
| Fresh against frozen | ||||
| Salting 15 minutes first | ||||
| Skin on or off | ||||
| Checking by sight and thermometer |
Troubleshooting
| Problem | Likely cause | What to do |
|---|---|---|
| Fish smells strongly of ammonia | Old fish | Don't eat it; buy fresher fish |
| Fish sticks to the pan | Pan not hot, wet fish or moved too soon | Dry the fish, heat the pan, and leave it until it releases |
| Dry, chalky fish | Overcooked | Cook until just opaque; rest briefly |
| Fish falls apart | Handled too much or overcooked | Use a wide fish slice and turn once |
| Soggy coating | Fish not dried or tray not hot | Pat dry and preheat the tray |
| Pâté bitter or very salty | Smoked fish very salty | Add more cream cheese or lemon; skip salt |
Raw fish, leftovers and allergens
Raw fish: keep raw fish on its own board and plate, away from food that won't be cooked. Wash your hands, boards and knives in hot soapy water afterwards, and store raw fish on a plate on the bottom shelf of the fridge so it can't drip onto other food.Leftover fish: cool cooked fish quickly, refrigerate it within 1 to 2 hours, and eat it within about 1 day (2 at most). Reheat only once, until steaming hot all the way through. Do not refreeze fish that was frozen and thawed unless you cook it first.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Checkpoint: can you do this now?
- I can tell fresh fish from old.
- I can store fish safely and cook it soon.
- I can check for pin bones and pat fish dry.
- I can tell when fish is cooked through.
- I know the main groups of fish.
Next chapter
Cooking Skills: Fish and Shellfish 1, chapter 2 is Pan-Frying Fish: a dry fish, a hot pan and not moving it.