To make the pastry, rub butter into the seasoned flour until it resembles breadcrumbs.
Add egg and mix with a knife to form firm dough. Add a little cold water if absolutely necessary to bring the dough together. It should come away cleanly from the sides of the bowl. Pre -heat oven to 190C
Cool pastry for 30mins is possible.
Roll out pastry on a lightly floured surface and use to line a flan dish. Trim pastry. Prick the base with a fork.
Place on a baking tray and bake (empty) for 10mins. until baked but not browned. Remove from oven. Turn down oven to 160C.
Flake trout over the pastry base. Combine the eggs with milk and dill. Pour into flan case over trout. Scatter with cheese.
Bake for approx 20mins until filling is set. Remove from oven. Serve warm or cold.