These are the ingredients for 1 (9 inch) pie. Scale accordingly.

1 (9 inch) refrigerated pie crust
2 teaspoons butter
3 leeks, chopped
1 pinch salt and black pepper to taste
1 cup light cream
1 1/4 cups shredded Gruyere cheese

Preheat oven to 375 degrees F (190 degrees C).
Melt butter in a large saucepan over medium-low heat. Stir in leeks; cook, stirring occasionally, for about 10 minutes, or until soft. Season with salt and pepper. Reduce heat to low. Stir in cream and cheese, and warm through. Pour mixture into pie shell
Bake in preheated oven for 30 minutes, or until custard is set and golden on top. Allow to sit 10 minutes before cutting pie into wedges.