Smoked Fish and Leek Pie

For the pastry: pile flour on the work surface, make a well in the center. Cut butter into small pieces and arrange around the well. Add egg and 1 teaspoon of salt to the well. Knead quickly into a smooth pastry, wrap in plastic wrap and refrigerate for 1 hour. 

For the topping: cut leeks lengthwise, rinse and cut into strips. Heat butter in a pan and saute leeks for about 5 minutes. Remove from heat and let cool.

Tear salmon and mackerel fillets into small pieces and mix with leeks.

Whisk eggs with crème fraîche and cream, season with a little salt, pepper and nutmeg.

Line baking pan (about 20 x 20 cm) (approximately 8 x 8 inches) with parchment paper.

Roll out about 2/3 of pastry and line baking pan with it, making an edge all around. Spread with fish and leek mixture and then with cream mixture. 

Roll out remaining pastry and cut into 1 cm (approximately 1/2 inch) wide strips. Arrange on top of a pie in a lattice pattern and press the edges together. Whisk egg yolk with milk and brush pastry with the mixture. 

Bake in preheated oven at 200°C (approximately 400°F) for about 45 minutes or until golden brown.