Pommes de Terre Marquise

Pommes de Terre Marquise (tomato-tinted duchesse potatoes) teaches the discipline of reduction. The one true thing to know before you touch the pan is this: the tomato purée must surrender nearly all its water before it meets the potato. Leave it loose and the handsome half-eggs slump; reduce it to a dense, brilliant paste and their grooves stand proud while the egg gilding bronzes.

The classical kitchen assumed Pommes Duchesse ready in quantity, a saucier, the sauce cook, reducing tomato by eye, and sheet pans moving through service; a salamander might finish the colour, but this entry sends the shapes to a somewhat hot oven. At home, use one pound of prepared Pommes Duchesse, a small saucepan, one grooved piping tip, and the hot upper third of an ordinary oven, with the broiler only if the ridges need a final touch. The brigade's holding and tray-scale work was scaffolding, so it goes; the exact tomato ratio, firm piping, light gild, and last-minute bake are the dish, so they stay. One cook, one stove, one evening.

You are after eight plump, ridged shapes, red-gold at the tips and tender beneath, generous rather than dainty. Reduce first, measure second: those three tablespoons of finished purée per pound of Pommes Duchesse decide everything.