Vegetarian Shepherd's Pie

Finely dice the onion, carrots, and celery. Finely chop the mushrooms. Mince the garlic. Peel and cut the potatoes and celeriac into chunks. Measure out the lentils, wine, stock, and all remaining ingredients.

Place the lentils in a saucepan and cover with cold water by 5 cm. Bring to a boil over high heat, then reduce to a steady simmer and cook for 20 minutes until just tender but not collapsing — they will continue cooking in the filling. Drain and set aside.

Heat the olive oil in a large, deep ovenproof skillet or casserole over medium-high heat until shimmering. Add the mushrooms in a single layer and cook without stirring for 5 minutes until deeply browned and all moisture has evaporated — you should hear active sizzling, not steaming.

Push the mushrooms to the edge of the pan, reduce heat to medium, and add the onion, carrots, and celery. Cook for 8 minutes, stirring occasionally, until the vegetables are soft and lightly golden.

Add the garlic, tomato purée, smoked paprika, and thyme. Stir constantly for 2 minutes until the purée darkens from bright red to a rusty brown.

Pour in the red wine and scrape up any browned bits from the base of the pan. Cook for 3 minutes until the wine is almost fully reduced and the pan looks nearly dry.

Add the drained lentils, vegetable stock, Worcestershire sauce, and bay leaves. Stir to combine, then simmer over medium-low heat for 15 minutes until the sauce is thick, glossy, and just coats the lentils — it should not be soupy. Remove the bay leaves and season generously with salt and pepper.

While the filling simmers, place the potato and celeriac chunks in a large saucepan, cover with well-salted cold water, and bring to a boil over high heat. Cook for 15 minutes until completely tender when pierced with a knife.

Drain the potato and celeriac thoroughly, return to the hot pan, and shake over low heat for 1 minute to drive off any remaining moisture. Pass through a potato ricer or mash until completely smooth.

Beat the butter, warm milk, and egg yolk into the mash until silky. Season generously with salt and white pepper. Set aside.

Preheat your oven to 200°C (fan 180°C / gas mark 6).

Spoon the lentil filling evenly into a deep 28 × 20 cm baking dish if not using the skillet. Spread the mash over the top in an even layer, then use a fork to drag the surface into ridges — these catch and brown in the oven.

Scatter the grated cheese evenly over the mash. Bake for 25 minutes until the top is deeply golden and the filling is visibly bubbling at the edges.

Rest for 5 minutes before serving — this allows the filling to set slightly so it holds when portioned.