Onions, Garlic and Alliums
Cooking Skills: Knife Skills 1
Chapter 2 · Onions, Garlic and Alliums
Skill goal
Dice an onion, slice evenly, crush garlic and wash and cut leeks.
Shopping list for this chapter
The basics
Onions, garlic, shallots, leeks and spring onions (the alliums) are the start of most savoury cooking. They are also the first thing most people have to learn to cut, and the one that makes them cry.
Dicing an onion
- Halve it through the root, from top to bottom. Cut off the stalk end, but leave the root: it holds the layers together.
- Peel off the skin and outer layer, and lay a half flat side down.
- Horizontal cuts: with the knife parallel to the board, make 1 to 3 cuts from the stalk end towards the root, stopping short of it. (Optional: for a fine dice, make two or three; for a rough dice, none.)
- Vertical cuts: cut from top to bottom towards the root, with spacing as wide as you want the dice.
- Cut across to make the dice. Throw away the root.
Garlic, shallots and leeks
| Food | Cut | How |
|---|---|---|
| Garlic | Crush | Press the flat of the blade down on the clove; the skin slips off |
| Garlic | Slice or mince | Slice thin, then chop across; or rock the knife over a pile |
| Garlic | Paste | Mince with a pinch of salt, then press and drag the flat of the blade |
| Shallot | Dice | Like an onion, but smaller |
| Leek | Half-rings | Halve lengthways, wash between the layers, then slice across |
| Spring onion | Rings or diagonal | Trim the roots and tough tops, slice thin |
- Why onions make you cry: cutting releases a gas that irritates the eyes. A sharp knife damages fewer cells, a cold onion releases less, and a good ventilated space helps. Chilling the onion for 20 minutes helps a little.
- A sharp knife is the best onion tool.
- Garlic burns easily when cooked: add it to the pan after the onions, for 30 to 60 seconds.
Try it
Level 1 · Start here
Quick pickled red onion
A red onion sliced thin and soaked in vinegar goes bright pink and sharp-sweet. Even thin slices matter: thick pieces stay harsh.
Ingredients (4 portions)
- 1 medium red onion
- 100 ml cider or white wine vinegar
- 100 ml water
- 1 tbsp sugar
- 1 tsp salt
- Cut the onion in half from root to tip. Peel off the skin, and cut off the stalk end only (leave the root, which holds the layers together).
- Lay each half flat side down and slice thinly from stalk to root, into half-moons about 2 mm thick. Cut off the root at the end.
- Warm the vinegar, water, sugar and salt in a small pan or microwave until the sugar dissolves. Pour over the onions in a jar and press them down.
- Leave for at least 30 minutes. Keep in the fridge, covered, and use within a week.
Level 1 · Garlic
Garlic and herb dressing
Fresh garlic can be harsh raw. Crushing it with salt into a paste spreads it through the dressing evenly instead of leaving harsh lumps.
Ingredients (4 portions)
- 2 garlic cloves
- ¼ tsp salt
- 1 lemon, juice (about 3 tbsp)
- 4 tbsp extra-virgin olive oil
- 2 tbsp finely chopped parsley
- 1 tsp Dijon mustard (optional)
- 1 pinch black pepper
- Lay the garlic cloves on the board and press down hard with the flat of a chef's knife until they crush. Peel off the skins, and chop the cloves finely.
- Sprinkle over the salt. Press and drag the flat of the knife over the garlic repeatedly until it turns into a smooth paste.
- Scrape into a bowl. Whisk in the lemon juice, mustard and pepper, then the oil, then stir in the parsley.
Garlic in oil
Raw garlic kept in oil at room temperature can grow the bacteria that cause botulism. Make this dressing fresh, keep it in the fridge, and use it within 2 days.
Level 2 · Slice
Simple onion soup with cheese toast (no wine)
Slice the onions thin and even, so they cook down at the same rate. The soup gets its flavour from slow, gentle softening.
Ingredients (2 portions)
- 3 onions (about 450 g), halved and thinly sliced
- 1 tbsp olive oil
- 15 g butter
- 1 pinch salt
- 1 tsp thyme leaves
- 500 ml hot beef or vegetable stock
- 2 slices of bread
- 40 g Gruyère or Cheddar, grated
- Halve and peel the onions. Slice each half into thin half-moons, about 3 mm thick, root to stalk. Cut away the root.
- Heat the oil and butter in a wide pan over a low heat. Add the onions and salt and cook for 30 to 35 minutes, stirring every few minutes, until soft, sweet and golden brown.
- Add the thyme and stock, bring to the boil, then simmer for 10 minutes.
- Toast the bread, top with the cheese and grill until bubbling. Ladle the soup into bowls and float the toast on top.
Level 2 · Leeks
Leek and spring onion frittata
Leeks hide grit between their layers, so they need washing as well as cutting. Cut the spring onions on the diagonal for a pretty finish.
Ingredients (2 portions)
- 1 medium leek, trimmed
- 3 spring onions
- 1 tsp olive oil
- 4 Lion-marked eggs
- 30 g Cheddar, grated
- 1 pinch salt and pepper
- Trim the root and the tough dark green top off the leek. Cut it in half lengthways, fan the layers under running water to wash out any soil, and shake dry. Slice into thin half-rings, about 3 mm.
- Slice the spring onions thinly on the diagonal. Keep a few for the top.
- Soften the leek in the oil in an ovenproof frying pan for 5 to 6 minutes over a medium-low heat. Add the spring onions for 1 minute.
- Beat the eggs with the cheese and seasoning. Pour over the vegetables and cook on a low heat for 4 to 5 minutes, until the edges are set. Finish under a hot grill for 2 to 3 minutes until set all the way through and lightly golden.
Experiments
Experiment
Root on or off
Why leave the root?
- Dice one onion half with the root left on until the end. Cut the root off another half before dicing.
- Compare how well the layers hold together.
Look for: With the root on, the layers stay together and cut into neat dice. Without it, the layers slide apart and the pieces go uneven.
Experiment
Chilled onion
Does it help the tears?
- Chill one onion in the fridge for 20 minutes. Dice it and a room-temperature one, side by side.
- Notice how much your eyes sting.
Look for: The chilled onion is usually less irritating, though the effect varies by person and onion.
Experiment
Fine or rough dice
How does the cut change the cooking?
- Make two small pans of softened onion, one fine dice and one rough dice, cooked for the same time.
- Compare how soft and how browned each is.
Look for: The fine dice cooks and browns faster and melts into a sauce. The rough dice stays in pieces and takes longer.
Experiment
Garlic crushed, minced or sliced
How does the cut change the taste?
- Make three small spoonfuls of the dressing with garlic that is crushed to a paste, finely minced, and thinly sliced.
- Taste each on a piece of bread.
Look for: The paste is the strongest and most even. Minced is strong but patchy. Sliced is mild and gives occasional bites of garlic.
Tasting notes
| What I tried | Method or amount | What I saw | What I thought | Will I do it again? |
|---|---|---|---|---|
| Quick pickled red onion | ||||
| Garlic and herb dressing | ||||
| Onion soup | ||||
| Leek and spring onion frittata | ||||
| Root on vs off | ||||
| Chilled vs room-temperature onion | ||||
| Fine vs rough dice | ||||
| Garlic: paste, minced, sliced |
Troubleshooting
| Problem | Likely cause | What to do |
|---|---|---|
| Dice are uneven | Cuts too far apart, or root cut off early | Keep the root; cut evenly spaced |
| Layers slide apart | Root removed | Leave the root until the end |
| Streaming eyes | Blunt knife, or a strong onion | Sharpen; chill; ventilate |
| Garlic bitter | Burnt in the pan | Add late; keep the heat moderate |
| Gritty leeks | Not washed between the layers | Halve and fan under running water |
| Soup pale | Onions not cooked long enough | Cook slowly for 30 to 35 minutes |
Knife and food safety
Knife safety: a sharp knife is safer than a blunt one, because it needs less force and slips less. Always cut on a stable board (put a damp cloth underneath), tuck your guiding fingertips back (the claw), carry a knife with the point down and the edge away from you, and never try to catch a falling knife: step back and let it fall. Wash knives by hand and dry them at once; never leave one in a sink of water where you can't see it. Store them in a block, on a magnetic strip or in guards, not loose in a drawer. A cut-resistant glove on your guiding hand is a sensible aid while you learn. If you cut yourself, apply firm pressure with a clean cloth, and get medical help for a deep cut or one that won't stop bleeding.Onions are slippery once cut: use the flat side as the base. Garlic in oil is a botulism risk at room temperature: keep garlic-and-oil mixtures in the fridge and use them within 2 days. Frittata must be set all the way through; use Lion-marked eggs.
Hygiene: wash your hands, boards and knives in hot soapy water after handling raw meat, fish or eggs, and don't use the same board for raw meat and for food that won't be cooked. Wash fruit, vegetables and herbs that you eat raw.
Leftovers: cool cooked food quickly (within 1 to 2 hours), keep it covered in the fridge, and eat it within 2 days. Reheat until steaming hot all the way through, and only once.
Checkpoint: can you do this now?
- I can dice an onion with the root left on.
- I can slice onions thinly and evenly.
- I can crush and mince garlic.
- I can wash and slice a leek.
- I know how to store garlic dressings safely.
Next chapter
Cooking Skills: Knife Skills 1, chapter 3 is Herbs, Zest and Soft Things: chopping herbs, chiffonade, zest and citrus segments.