Place oil in a frying pan and gently cook leeks for 3-4 mints until soft. Remove and cool.
Mix ricotta & egg in a mixing bowl to combine, season well with salt and pepper. Stir through salmon leeks and potato.
Lay one sheet of puff pastry onto a lightly greased baking tray. Spoon filling into the middle. Brush edges with egg wash and top with other sheet of pastry. Press edges together with a fork & cut 3 vents in top of pie.
Decorate with extra pastry and brush with egg wash.
Bake for 30-35 minutes until light brown and crisp. Serve warm or cold with a mixed salad.