Method
For the pastry, sift the flour into a bowl and rub in the butter until the mixture resembles fine breadcrumbs. Stir in the salt, then mix to a dough with the egg yolks and a little cold water if necessary. Roll the pastry out and line a tin. To bake blind, cover the pastry with greaseproof paper and fill with baking beans. Bake in an oven preheated to 180ºC / Gas 5 for 20 minutes.
Meanwhile, for the white sauce, melt the butter, add the flour and cook gently until the roux leaves the side of the pan (no colour). Gradually add the milk to form a sauce, then add the grated cheese and stir until melted.
Remove the pastry from the oven, take out the beans and greaseproof paper and brush with lightly beaten egg white before returning to the oven for 5–10 minutes.
Prepare the leeks and heat the butter in a pan. Add the leeks and two tablespoons of water, cover and cook gently until soft. Season with salt and pepper and leave to cool.
Place the smoked haddock in the cooked pastry case. Combine the leeks with the white sauce and pour over the fish. Bake in the oven for 15–20 minutes until lightly set.
Serve with a rainbow salad of red onion, red and yellow peppers, salad leaves and baby potatoes.