One-pot potato gratin with cheese and pancetta (gratin savoyard-style home version)

Pour cold milk and cold cream into a big pan; potatoes must start in cold liquid or they overcook outside.

Peel the potatoes, cut in rather thick slices and put them straight into the milk and cream so the starch goes into the liquid.

Season with rock salt, a pinch of nutmeg and black pepper, and add the garlic and onions.

Over medium heat, stirring, bring very gently to the boil, then pre-cook 8 to 15 minutes depending on thickness (about 10 here), until easy to cut with the back of a knife.

Turn off the heat and let rest on the back of the stove; pan fry a few slices of pancetta in a little oil.

Lift a layer of potatoes with a sieve into an enamel dish, add pancetta, then cover with more potatoes.

Pour over just enough of the milk and cream, then cover all the potatoes generously with cheese.

Cook 30 minutes in the oven at 180 to 200C.

Alternatively start at 350F for 15 minutes, then raise the temperature for the last 15 minutes for a brown, crusty cheese top.

Let it rest, at least an hour, so the milk and cream go back into the potatoes.