For the pastry, sift the flour and salt into the bowl of a food processor, add the butter and lard, then whizz together briefly until the mixture looks like fine breadcrumbs
Tip the mixture into a bowl, then stir in the cheese and enough of the water for the mixture to come together
Tip out onto a lightly floured surface and knead briefly until smooth
Roll out thinly and line a 23cm x 4cm loose-?bottomed fluted flan tin
Prick the base with a fork
Chill for 20 minutes
02
Melt the 75g butter in a saucepan over a low heat, then add the leeks and the salt
Cover and cook for ?10 minutes until soft
Uncover the pan, increase the heat and cook ?for 2 minutes, stirring occasionally, until the liquid has evaporated
Spoon onto a plate and leave to cool
03
Preheat the oven to 200°C/fan180°C/gas 6
Line the pastry case with baking paper and baking beans or rice and blind bake for 15-20 minutes until the edges are biscuit-coloured
Remove the paper and beans/rice and return the case to the oven for 7-10 minutes until the base is crisp and lightly golden
Remove and set aside
Reduce the oven temperature to 190°C/fan170°C/gas 5
04
Put the crème fraîche into a bowl with the whole egg, egg yolks and nutmeg
Lightly beat together, then season
Stir in the leeks
Spoon ?the mixture into the tart case and bake for 35-40 minutes until set ?and lightly golden