Gratins and Potato Bakes

Cooking Skills: Potatoes 1

Chapter 7 · Gratins and Potato Bakes

Skill goal

Slice potatoes evenly and bake them in a liquid until tender with a golden top.

The basics

A gratin is potatoes cooked in a liquid until they are tender, with a golden top. The skills are even slicing, the right liquid, and the right temperature: low and slow, so the middle cooks before the top burns.

Version	Liquid	Character
Stock-baked layers	Stock	Light and savoury
Boulangère	Stock and onions	Sweet and mellow
Lighter milk gratin	Milk	Creamy but lighter
Dauphinoise	Cream and milk	Rich and luxurious

Slice evenly, about 3 mm. A mandolin is best. Use its guard or a cut-resistant glove: mandolins cause many kitchen injuries.
Don't rinse the slices in cream-based gratins. The starch thickens the sauce.
All-rounder or waxy potatoes keep their shape; floury ones fall apart.
Rest for 10 minutes so the bake sets.

Try it

Level 1 · Start here

Stock-baked potato layers

1 hour 30 minutes3 to 4 portionsno cream, just stock

The simplest bake: sliced potatoes baked in seasoned stock until tender, with the top browned. Light, and a good starting point.

Ingredients (4 portions)

600 g all-rounder or waxy potatoes (e.g. Desiree), peeled and sliced 3 mm thick
300 ml hot vegetable or chicken stock
1 tsp butter, for the dish
1 garlic clove, crushed
1 tsp chopped thyme
1 pinch salt and pepper

Heat the oven to 180°C fan (200°C conventional, gas 6). Butter a 1.5 litre baking dish and rub it with the garlic.
Slice the potatoes evenly (a mandolin is best, with its guard; otherwise a sharp knife). Layer them in the dish, seasoning each layer and scattering over the thyme.
Pour in the hot stock until it just reaches the top layer.
Cover with foil and bake for 40 minutes. Remove the foil and bake for 25 to 30 minutes, until golden and a knife slides in easily.

Level 2 · French

Boulangère potatoes

1 hour 45 minutes4 portionspotatoes and onions in stock

A French baker's dish: potatoes layered with softened onions and baked in stock. The onions give it a mellow sweetness.

Ingredients (4 portions)

600 g all-rounder potatoes, peeled and sliced 3 mm thick
2 onions, thinly sliced
1 tbsp olive oil
1 tsp butter, plus a knob for the top
350 ml hot vegetable or chicken stock
1 tsp thyme leaves
1 pinch salt and pepper

Soften the onions in the oil and butter over a low heat for 10 to 12 minutes, until soft but not browned.
Heat the oven to 180°C fan (200°C conventional, gas 6). Layer the potatoes and onions in a buttered dish with seasoning and thyme, finishing with a layer of overlapping potato slices.
Pour over the hot stock, dot the top with butter and cover with foil.
Bake for 45 minutes, uncover, and bake for 25 to 30 minutes more until golden.

Level 3 · The treat

Dauphinoise

1 hour 45 minutes4 portionsrich: a treat

The famous gratin. Potatoes simmered briefly in cream and milk, then baked until the top is golden and the cream has thickened. Rich enough to be a meal in itself with a salad.

Ingredients (4 portions)

600 g all-rounder potatoes, peeled and sliced 3 mm thick
300 ml double cream
150 ml whole milk
2 garlic cloves, crushed
1 pinch nutmeg
1 tsp butter, for the dish
1 pinch salt and pepper

Heat the oven to 160°C fan (180°C conventional, gas 4). Butter a 1.5 litre dish and rub it with a little of the garlic.
Put the cream, milk, remaining garlic, nutmeg and seasoning in a large pan. Add the potato slices (don't rinse them: the starch thickens the sauce) and bring to a gentle simmer for 5 minutes, stirring carefully so they don't break.
Transfer the slices and cream to the dish, spreading in even layers. Press down lightly.
Bake for 1 hour to 1 hour 15 minutes, until golden, bubbling and a knife slides in easily. Rest for 10 minutes before serving.

Why simmer first

Pre-cooking the slices in the cream heats them evenly, so they cook faster and the cream doesn't curdle in the oven.

Level 2 · Lighter

Lighter milk gratin

1 hour 30 minutes4 portionsa lighter dauphinoise

The same method with milk instead of cream, and a little cheese on top for browning. It can curdle slightly, but still tastes good.

Ingredients (4 portions)

600 g all-rounder potatoes, peeled and sliced 3 mm thick
400 ml semi-skimmed milk
1 bay leaf
1 garlic clove, crushed
30 g Gruyère or mature Cheddar, grated
1 tsp butter, for the dish
1 pinch nutmeg, salt and pepper

Heat the oven to 160°C fan (180°C conventional, gas 4). Heat the milk with the bay leaf, garlic, nutmeg and seasoning until steaming, and let it infuse for 5 minutes.
Layer the potatoes in a buttered dish and pour over the milk (remove the bay leaf).
Cover with foil and bake for 45 minutes. Uncover, sprinkle with the cheese and bake for 30 minutes more, until golden and tender.

Experiments

Experiment

Slice thickness

How thin?

Make three small gratins in ramekins with slices 2 mm, 4 mm and 8 mm thick, all with the same liquid.
Bake together and test with a knife every 10 minutes.

Look for: The thin slices turn soft and can become mush. The thick ones stay firm in the middle. About 3 mm is a good balance.

Experiment

Pre-cook or not

Is the simmer worth it?

Make two small dauphinoise. Simmer the slices in the cream first for one; layer the other raw with the cream poured over.
Bake both for the same time.

Look for: The simmered gratin is evenly cooked and thick. The raw one takes longer and may have firm potato underneath.

Experiment

Cream, milk or stock

How much richness?

Bake three small gratins with cream, milk and stock.
Taste them.

Look for: Cream is rich and smooth, milk is lighter but can split, stock is savoury and clean. All are good; they are different dishes.

Experiment

Rest or serve at once

Does resting help?

Cut a slice straight from the oven and another after 10 minutes.

Look for: The rested slice holds together and the sauce has thickened. The hot slice slumps.

Tasting notes

What I tried	Method or amount	What I saw	What I thought	Will I do it again?
Stock-baked layers
Boulangère
Dauphinoise
Lighter milk gratin
Slice thickness
Pre-cook vs raw
Cream, milk, stock
Rested vs not

Troubleshooting

Problem	Likely cause	What to do
Still hard in the middle	Slices too thick or oven too cool	Slice thinner; cover with foil; bake longer
Curdled or split sauce	Milk, high heat, or acid	Bake low and slow; use cream or add a little flour
Watery	Rinsed slices, or too much liquid	Don't rinse; liquid should just reach the top
Top burnt, middle raw	Oven too hot	Lower the heat and cover with foil
Grey slices	Peeled and left to stand	Slice just before assembling
Greasy	Too much cheese or cream	Use less or switch to stock

Food safety: slicing and storage

Mandolin slicers are sharp and a leading cause of kitchen injuries: always use the guard or a cut-resistant glove, and stop when the potato gets small. Raw potatoes: keep them somewhere cool, dark and dry (above about 6°C), not in the fridge and not in the light. The Food Standards Agency advises against keeping raw potatoes in the fridge if you will roast or fry them, because the cold raises the amount of acrylamide that forms when they brown. Light turns the skin green and makes sprouts, and the green and the sprouts contain a natural toxin (solanine) that is bitter and can upset your stomach. Cut away sprouts and any green patches generously; if a potato is green all over, or tastes bitter, throw it away. Cooking does not remove it.

Gratins keep a lot of heat and cool slowly, so cut into portions and spread out to cool within 1 to 2 hours. Cooked potatoes: cool them quickly (spread out, within 1 to 2 hours), keep them covered in the fridge, and eat them within 2 days. Reheat until steaming hot all the way through, and only once. (This is the general chilled-leftovers advice relayed by local-authority food-safety pages; unlike rice, potatoes have no special rule of their own, but they are starchy, so they are treated with the same care.)

Checkpoint: can you do this now?

I can slice potatoes evenly and safely.
I can make a stock-baked gratin.
I can make a dauphinoise.
I know why I don't rinse the slices.
I know the bake needs to rest.

Next chapter

Cooking Skills: Potatoes 1, chapter 8 is Soups, Salads and Cakes: potatoes as a base and a binder.