Teurte de Pommes de Terre Berrichonne

Make the pastry: combine the flour and half the salt in a large bowl, then rub in the cold cubed butter with your fingertips until the mixture resembles coarse breadcrumbs. Add the egg yolks and ice-cold water a tablespoon at a time, pressing the dough together until it just coheres — do not overwork it. Divide into two discs, one slightly larger than the other, and wrap.

Refrigerate the pastry discs for at least 1 hour until thoroughly chilled and relaxed.

Melt the 30 g butter in a wide frying pan over medium-low heat. Add the sliced onions with a pinch of salt and cook, stirring occasionally, for 25–28 minutes until deeply golden, soft, and sweet. Add the garlic and cook for a further 2 minutes until fragrant, then remove from the heat and allow to cool.

In a large bowl, toss the sliced potatoes with the sweated onion mixture, parsley, thyme leaves, nutmeg, black pepper, the remaining salt, and the 200 ml crème fraîche until thoroughly combined.

Preheat the oven to 200°C, or 180°C for a fan oven, or gas mark 6. Butter a 24 cm round, deep pie dish or earthenware tian generously.

On a lightly floured surface, roll the larger pastry disc to a circle roughly 32 cm in diameter and line the prepared dish, pressing gently into the corners and leaving overhang. Fill with the potato mixture, mounding it slightly in the centre. Roll the second disc to 26 cm and lay over the top as a lid.

Trim the pastry overhang to 2 cm, fold it up and crimp firmly to seal. Cut a 2 cm diameter hole in the centre of the lid for steam to escape — fashion a small foil chimney to keep it open. Brush the entire surface with the beaten egg wash.

Bake on the middle shelf of the preheated oven for 30 minutes until the pastry is set and beginning to colour.

Reduce the oven temperature to 170°C, or 150°C for a fan oven, or gas mark 3 and bake for a further 40 minutes until the pastry is a deep golden brown and a skewer inserted through the vent meets no resistance from the potatoes.

Remove from the oven and immediately pour the 3 tablespoons of crème fraîche through the chimney vent using a small spoon or funnel. Leave to rest for 10 minutes before cutting into wedges and serving directly from the dish.