Pommes de terre au lard

Prepare the potatoes. Peel 1,000 g purchased potatoes to obtain about 900 g, slice them evenly to 4 mm and keep the slices together rather than rinsing away all surface starch. The slices are even, dry on the surface and still intact. Even slices finish together and a little starch helps the layers bind. Use a hand guard with a mandoline and keep fingertips behind the blade.

Render the bacon. Set the bacon in a cold 28 cm heavy lidded casserole, then cook over medium-low heat for 8 minutes, stirring occasionally, until much of the fat is rendered and the edges begin to colour. The bacon has released a glossy layer of fat and the edges are lightly browned. A slow render seasons the potatoes without scorching the cured pork. Commercially prepared bacon still requires safe handling; the later covered cook and final 5-minute rest exceed the 63 °C plus 3-minute intact-pork minimum.

Soften the onions. Add the onions and 20 g butter to the rendered bacon and cook over medium-low heat for 7 minutes, stirring, until the onions are soft but not deeply browned. The onions are translucent and supple, with no dark scorched edges. Soft onions distribute sweetness and moisture through the potato layers. Hot rendered fat can spit; add the onions carefully.

Build the casserole. Take the pan off the heat. Layer the sliced potatoes over the bacon and onions, dotting with the remaining 20 g butter. Add the 100 ml wine and 100 ml broth around the edge, then season with pepper and at most 1 g salt. Return to medium heat for 5 minutes. Steam is rising steadily and liquid is just beginning to simmer around the edges. Bringing the liquid to a simmer before the oven starts the covered braise evenly. Taste the cooking liquid before adding salt because cured bacon varies sharply in salinity.

Cook covered. Cover tightly and cook at 190 °C for 45 minutes without stirring the layers. A thin knife slides through a central potato slice with only slight resistance. Covered cooking softens the centres without breaking the slices apart. Use dry oven gloves; the lid, steam and rendered fat are burn hazards.

Brown the top. Uncover and continue at 190 °C for 10 minutes, until the top layer takes on light golden patches and the cooking liquid is mostly absorbed. The top potatoes show golden edges while the lower layers remain moist, not soupy. A short uncovered finish gives colour without turning the dish into a crisp fry. Keep the casserole stable when removing the hot lid.

Rest before serving. Remove the casserole from the oven and rest it uncovered for 5 minutes before portioning. The bubbling subsides and the potato layers hold together when lifted. The pause lets starch and fat settle and also completes the mandatory intact-pork rest interval. Do not serve the bacon before the full rest has elapsed.