Potato Gratin

Potatoes: don't reach for the ones you'd use for roasting on a Sunday. Those are floury — Maris Piper, King Edward — bred to fluff up and crisp outside, which in a gratin means they collapse into mush, because floury potatoes break down under heat instead of holding their shape. You want a waxy potato — Désirée, Charlotte, even a supermarket 'salad potato' bag — one that keeps its slice-shape through the bake while still shedding enough surface starch to thicken the cream. Myth worth killing here: 'any potato does' — no, because the whole dish depends on this one trade-off, structure versus starch, and waxy gives you both.

Cream: double cream because fat content is what keeps it from splitting at oven heat and what gives you that thick, almost custard-set texture once it cools a touch. If you're out of double cream, the criterion is high fat and low water — crème fraîche works, thinned slightly with milk if it's very thick; single cream or milk alone will separate and run thin, no matter how long you bake it, because there isn't enough fat to hold the emulsion together.

Garlic: rubbed into the dish, not sliced into the layers. Rubbing leaves aroma without leaving you a mouthful of raw garlic halfway through a bite of cream and potato — a small thing, but it's the difference between background perfume and someone complaining at the table.

Cheese: mature cheddar earns its place here because it's dense and low in moisture — it browns into a crust rather than weeping water into your cream. A young, wet cheese — mozzarella, a soft Brie — would do the opposite: melt into strings or pools and leave the top soggy instead of golden. If cheddar isn't in the fridge, any hard, dry cheese that grates rather than squishes will do the same job — a mature Gruyère, an aged Lancashire.

Nutmeg and salt are the quiet workers. Nutmeg isn't decoration — it's the traditional partner to dairy-heavy dishes precisely because its slight bitterness cuts the flatness of a lot of cream, the same reason it turns up in béchamel. A pinch, grated fresh if you have a whole nutmeg knocking about in a spice drawer — pre-ground loses its edge within months of opening the jar.

Last thing: patience, the ingredient the recipe card never lists. Once it's out of the oven, the cream is still a liquid holding its shape by heat alone. Cut into it straight away and it runs across the plate like a burst dam. Give it ten minutes standing — the starch finishes setting as it cools, and what was sauce becomes something you can lift out in a clean wedge. This waiting is not optional; it's the difference between a gratin and a potato soup with delusions of grandeur.