Fry the chopped white part of the leeks in the butter until soft and remove it. In the same butter, successively fry the diced bacon and chicken, remove them and let them drain. Pour out the butter, return the leeks, bacon and chicken to the pan, add salt and pepper to taste.
Add the egg yolks beaten with the cream and leave on low heat for about 3 minutes, stirring constantly. Remove from the fire and sprinkle with parsley. Heat the oven to 410°F (210 °C). Cut the puff pastry into 2 sheets. Put one sheet in a greased baking tray.
Spread the filling on top while leaving about 3/4″ (2 cm) of space from the edge. Cover with the second sheet and press the edges together.
Brush with beaten egg and pierce with a fork to allow the steam to escape. Bake for about 30 minutes.