Preparation
Step 1
For the filling, cook the potato in a pan of boiling salted water for 8-10 minutes. Drain then leave to steam dry
Step 2
Heat the oil and butter in a large frying pan set over a medium heat. Fry the leeks for 5 minutes, stir in the flour then cook for 2 minutes more. Pour in the milk, a little bit at a time, stirring continuously to combine.
Step 3
Add the cream, cheese and mustard then cook for 1-2 minutes to melt the cheese. Season, stir in the chives then remove from the heat and cool for 15 minutes.
Step 4
While the mixture cools, prepare the dough. Turn out one of the dough discs on to a lightly floured surface then roll into a 30cm circle.
Step 5
Preheat the oven to 220C. Gently fold the tuna and potato in the leek mixture then spoon in to the dish. Drape the pastry over the pie, trim the excess and crimp the edges. (You can shape any offcuts to use as decorations.) Brush the top with the yolk then
Step 6
bake for 35-50 minutes until the pastry is crisp and golden. Serve with steamed greens and lemon wedges.
Step 7
Note: Keep the rest of the pie dough in the freezer to use for another recipe.
