Vegetarian

Pulse the plain flour and salt with the butter and lard in a food processor until the mixture resembles fine breadcrumbs
Tip the mixture into a bowl, stir in the cheddar cheese and enough water to bring the dough together, knead briefly, roll out thinly, line a 23cm x 4cm loose-bottomed flan tin, prick the base and chill for 20 minutes
Melt the 75g butter in a saucepan, add the leeks and salt, cover and cook until soft, uncover and increase the heat until the liquid has evaporated, then spoon onto a plate and cool
Preheat the oven to 400°F.
Line the pastry case with baking paper and baking beans or rice and blind bake at 400°F for 15–20 minutes until the edges are biscuit-coloured, remove the paper and beans/rice and return to the oven for 7–10 minutes until the base is crisp and lightly golden, then set aside and reduce the oven to 375°F.
Beat the crème fraîche with the whole egg, egg yolks and nutmeg, then season
Stir the cooled leeks into the crème fraîche mixture
Spoon the mixture into the tart case and bake at 375°F for 35–40 minutes until set and lightly golden.
Leave the tart for 10 minutes, remove from the tin and serve