Peel the potatoes and let cook with leeks (washed and cut).
Once cooked, sieved potatoes and seasoned with butter, salt and pepper to taste.
Add the capers, fresh grated pepper and mix.
Roll out the pastry on a baking sheet greased or covered with parchment paper.
Cover with the mashed potatoes and add the cheese diced.
Bake, in preheated oven, for 20 minutes at 180°C (350°F/ gas 4).