Tartiflette

Parboil the potatoes. Put 900 g potato cubes in cold water, bring to a gentle boil and cook until just tender at the edges but still firm in the centre, then drain and steam-dry. Timing: 12 minutes. Heat: medium-high then gentle boil. Temperature: boiling water. Partial cooking lets the potatoes finish in the cheese without collapsing. Drain carefully to avoid steam burns. A knife meets slight resistance in the centre and the cube edges remain intact.

Steam-dry the surface. Spread the drained potatoes briefly so surface steam can escape before assembly. Timing: 5 minutes active handling and steam-drying. Keep off the heat. Dry surfaces limit watery separation in the baking dish. The potato surfaces look dry rather than glossy with water.

Render the lardons. Render 200 g lardons in a large frying pan until lightly browned and the thickest pieces reach 71 °C. Timing: 5 minutes. Heat: medium heat. Temperature: 71 °C internal temperature. Rendering creates the cooking fat for the onions while the thermometer confirms pork safety. Avoid cross-contamination from undercooked pork. The lardons are lightly browned, have released visible fat and the thickest piece reaches 71 °C.

Soften the onions and reduce the wine. Add 200 g sliced onion to the rendered lardons and cook until soft without deep browning, then pour in 100 ml white wine and reduce until little free liquid remains. Timing: 10 minutes. Heat: medium heat. Temperature: simmering. Reducing the wine concentrates flavour and prevents a loose bake. Alcohol should not be assumed to evaporate completely. The onions are soft and translucent, and the wine has reduced so no watery pool remains in the pan.

Layer the dish. Layer the potatoes with the onion-lardon mixture and 2 g pepper in a 30 × 20 cm baking dish, distributing the rendered fat and reduced wine through the potatoes. Timing: 10 minutes. Even layering gives every portion potato, pork and sauce. The potatoes and lardon-onion mixture are evenly distributed with no dry corner or visible pool of liquid.

Bake under Reblochon. Set the two Reblochon halves over the potatoes with the rind facing up and bake until the cheese is fully melted, bubbling and the dish is hot throughout. Timing: 20 minutes. Heat: 200 °C conventional oven. Temperature: 200 °C. The hot bake melts the cheese into the pre-cooked potatoes without prolonged greasy separation. The cheese, dish and bubbling fat are extremely hot; use dry oven gloves. The Reblochon is fully melted beneath its browned rind, the edges bubble actively and the potatoes are tender throughout.