Preheat the oven to 180C/350F/Gas Mark 4
Sieve the plain flour into a large mixing bowl. Add the salt.
Rub the butter into the flour until the mixture resembles fine breadcrumbs. Add the egg and mix in enough cold water to bind the pastry together. Cover with cling film and rest until required.
Roll out the pastry and use it to line a 9 inch quiche dish.
Blind bake the shell for 15-18 minutes or until the pastry is lightly browned.
Meanwhile prepare the filling.
Fry the leeks and curly kale in a little oil for 2 minutes or until they are just softened, season with some salt and pepper.
Spread the vegetables over the pastry base.
Mix the eggs and milk together and add some seasoning, then pour over the top of the flan.
Sprinkle with the grated cheese and sliced brie and bake in the oven for 30-35 minutes.
Serve hot or cold with a mixed side salad.