Gratin of potatoes

By Birgitta

Heston Blumenthal

This can be made the day before: it is perfect for a barbecue, since it actually improves once rested and reheated. It is one of those recipes that’s deceptively simple, but takes a few tricks to get perfect.

The first secret is to simmer the potatoes in the flavoured milk before baking, in order to extract some of the starch. This gives them a creamy texture, while keeping the dish light. And by using the starch-thickened liquid, you can cut down on the amount of cream.

Slicing the potatoes thinly is also important, as it gives more surface area of potato and more flavour. A good gratin should be cooked for a long time at a low temperature. This will leave the potatoes as soft as butter while still holding their shape, and the sauce will be completely integrated.

And my final secret: once cooked, cover the slightly cooled gratin (with the foil still on) with a weighted dish. The potatoes will absorb any excess liquid overnight.

Remember, when cooking and reheating, the low temperature is important, otherwise the potatoes will split and become grainy. For this recipe, you will need a baking dish at least 2in deep, and about 10in long x 6in wide.

Ingredients

• 400 ml whole milk (or just enough to cover the potatoes in the pan)
• 3 fresh bay leaves (optional)
• 1 bunch of thyme (optional)
• 1 clove of garlic, crushed (or 2 tsp of garlic purée, if you have it)
• 1 kg potatoes, washed (red potatoes such as desiree or romano are good)
• 200 ml double cream
• 75 g unsalted butter
• Salt and cayenne pepper
• Nutmeg, grated, to taste

Preparation

Step 1

Preheat the oven to 120C/250F/Gas Mark.

Pour the milk into a saucepan and add the herbs (tied up in a piece of muslin) and the crushed garlic or garlic purée. On a medium heat, bring the milk to the boil and simmer it for 5 minutes. Remove from the heat, and leave to infuse. Once cool, remove the herbs. If you are not using herbs, simply combine the milk and garlic in the pan and set aside.

Peel the potatoes and slice them as thinly as possible. Use a mandolin, if you have one, or, alternatively, slice them with a knife, but watch your fingers. Ideally, the potato slices should be 1-2mm thick.

Add the sliced potatoes to the milk, separating them as you do so, and place the pan on a medium heat. Bring the liquid to a simmer, stirring occasionally to stop the potatoes from sticking together — you want to keep them as separate as possible. After a few minutes, you will notice that the milk has thickened with the starch from the potatoes. When this happens, add the cream and butter, and gently agitate the pan so that everything is mixed in.

Finally, add the salt, cayenne pepper and grated nutmeg. Be careful, as cayenne pepper is strong stuff. You will need to add more salt than you think necessary, as the potatoes do absorb quite a lot, leaving the gratin less seasoned once cooked.

Pour the potatoes into the oven dish, trying to get them as flat as possible. Use a perforated slice to press down on them. The potatoes should be covered by about ½cm of liquid. A little less is fine, but if you have more, don’t be tempted to use it all.

Tightly cover the dish with foil and bake in the oven for 4 hours. If you can, every 45 minutes or so, gently press down on the potatoes with the back of the slice.

Keep the gratin in the fridge until you are ready to use it. To reheat, warm at 150C/300F/Gas Mark 2 for about 40 minutes. Just before serving, flash the dish under the grill to gratinate.