FOR THE SHORTCRUST
250g plain flour
125g cold butter, diced

FOR THE FILLING
2 medium leeks
250g-300g undyed smoked haddock
500ml whole milk
100g mature cheddar cheese, grated
150ml double cream
2 large eggs plus 2 extra yolks
a pinch of cayenne pepper, optional

First, make the shortcrust. Pulse the flour, butter and a good pinch of salt in a food processor to a breadcrumb consistency. Tip into a bowl then gradually mix in 3-4 tablespoons chilled water until the dough starts to clump together. Bring together in a ball then knead the dough a couple of times. Wrap and chill for 30 minutes.

Heat the oven to 180°C, fan 160°C, gas 4. Roll the chilled dough into a round large enough to line a 23cm loose-based fluted tart tin, with an overhang. Prick the base, line with baking paper and baking beans then place on an oven tray and bake for 20 minutes or until set.

Remove the paper and beans and return to the oven for a further 10 minutes or until the base is dry and lightly golden. Trim off any overhanging pastry from the tart.
Meanwhile, cut away most of the darker green tops of the leeks (save them for making stock). Cut the remaining parts of the leeks into 2.5cm rounds on an angle. Wash them in plenty of water but be careful not to break up the rounds too much.

Place the smoked fish in a pan and pour over just enough milk to cover, bring to a simmer. Be sure not to boil the milk, and only cook for as long as it takes for the fish to flake (about 5 minutes). Lift the fish out of the milk using a slotted spoon and allow to cool. Add the drained leeks to the milk, pop a lid on the pan, just ajar, and bring up to a very gentle simmer. Cook for 6-8 minutes or until the leeks are tender. Lift the leeks out to a colander to drain, then transfer to a large mixing bowl. Flake the haddock into large pieces and add it to the bowl too, along with the grated cheese and some freshly ground black pepper then tumble everything together and spoon it into the prepared tart case on a baking tray, arranging it as evenly as you can.

Combine the cream, eggs and egg yolks in a bowl, then whisk in 200ml of the smoky, leeky milk and season lightly with salt and pepper. Pour the custard over the tart filling and give it a little jiggle to settle the fish and leeks into it. Dust with cayenne pepper if you like, then carefully place the tart in the oven. Bake the tart for 35 minutes or until set and a little blistered. Allow to cool for at least 25 minutes before serving.