Makes 1 quiche of 30cm

Start by making the pastry: put the flour and salt into a bowl. Cut the butter into cubes and add to the flour. Rub the butter and flour between your fingers until it resembles breadcrumbs. Add the egg and water and knead into a dough.
Shape the pastry into a disc, wrap in cling film and chill in the fridge for at least 2 hours.

After 2 hours, preheat the oven to 180°C fan.

Trim the leeks and cut off the dark green top, discard. Cut the leek into quarters lengthwise, then cut into slices so that you end up with approximately 350g. Put in a colander and wash under a running tap.

Melt the butter in a frying pan and fry the leek with a pinch of salt for 4 minutes until soft. Set aside.

Grease a 30cm quiche tin. Unwrap the pastry disc and put on a floured surface. Roll out the pastry with a rolling pin, so that the pastry is slightly larger than the quiche tin. Lift the pastry into the tin and press it firmly against the rim to make it stick. Cut off any excess pastry and prick the base with a fork.

Brush the mustard all over the pastry base, then distribute the leek all over.

To make the custard: put the Kachkéis into a jug and heat in a microwave until it’s slightly runny and easy to stir. Stir through the cream. Crack open the eggs in a bowl and beat. Add the beaten eggs to the Kachkéis and cream in the jug, season with pepper and ¼ tsp salt and mix.

Pour the custard over and quiche and top with the grated cheese.
Bake the quiche in the preheated oven for 40 minutes.