Boiled potatoes folded into a béchamel with parmesan, mozzarella and nutmeg, with bacon through it. Rich enough to be a main course rather than a side. Serves four.
Steps two and three are a béchamel, and it behaves like one. Equal weights of butter and flour, cooked together for a minute so the flour loses its raw taste, then the milk added while stirring. Cold milk into a hot roux is the reliable way to avoid lumps. Boil the potatoes until just tender and no further: they get stirred into a sauce afterwards and overcooked ones break up into mash. The sauce thickens as it stands, so serve it straight away or loosen it with a splash of milk before it goes to the table.