Pommes Boulangère

A dish of everyday French home and village cooking whose name — pommes à la boulangère, 'baker's-wife potatoes' — points to a real practice rather than a chef. In towns where households had no oven of their own, the dish of layered potatoes, onion and a joint of meat was carried to the village baker (boulanger) and slid into the bread oven as it cooled after the morning bake, cooking gently in the residual heat while the family was at church or at work. The same custom lies behind the Provençal daube and the Lancashire hotpot. Escoffier records pommes boulangère as a standard garnish; no single date or inventor attaches to so communal a dish.

The top slices curl up crisp and browned at the edges where they sat proud of the liquid, while the layers beneath are soft and glossy, soaked through with savoury, onion-sweet stock. It is altogether less rich than a cream gratin — cleaner, meatier, the flavour of good stock and slow-cooked onion running through every layer. Made under a roast, the bottom is darkened and concentrated with the rendered juices. A little chopped thyme and parsley lifts it.

With no cream to bind it, the dish relies on potato starch and reducing stock. Unrinsed slices leach starch that lightly thickens the stock as it cooks down, so the potatoes set together in a moist, sliceable mass rather than swimming loose. A waxy-to-all-purpose potato holds its slices; a very floury one disintegrates. The onions are usually softened in butter first to draw out their sweetness and stop them tasting raw. The dish is baked uncovered (or uncovered for the final stretch) so the exposed top dehydrates and browns by Maillard reaction while the interior steams tender in the stock.