Rub the butter into the flours until the mixture resembles fine breadcrumbs. Add 3 tablespoons milk and mix to a firm dough. Roll out on a floured work surface and use to line a 28 x 20 cm (11 x 8 inch) rectangular flan tin. Bake blind at 200 �C / 400 �F / Gas 6 for 10 minutes.

Cook the bacon in a non-stick frying pan until browned, remove and add the leeks to the pan. Cook until soft. Place the bacon, leeks and cheese in the flan case.

Beat together the eggs and milk, season and pour into the flan. Bake 180 �C / 350 �F / Gas 4 for 25 minutes until set. Cut into squares and serve hot or cold.