2 1/2 cups of leeks (white of 4 leeks, minced and washed) or 6 yellow onions
3 Tbsp of butter
salt, black pepper, nutmeg
1/4 to 1/2 cup of crème fraiche (heavy cream is ok)
q/4 cup of gruyere or swiss cheese
Puff pastry with 6 turns
Glaze: 1 egg yolk & 1/2 Tbsp of water

• Melt the butter in a pan until it sizzles. 
• Add leeks and coat them with the butter. 
• Season with salt, freshly ground pepper and a pinch of nutmeg.
• Cover and cook for 10 minutes over low heat.  Make sure the leeks do not burn.
• Pour the heavy cream and cook for another 15 minutes or until it thickens.
• Cool while you grate the cheese. 
• Mix together and refrigerate until cold.
• Cut two thirds of the puff pastry and refrigerate the rest. Then cut the two third piece in half.   Put the other half in the refrigerator.
• With some flour on the pastry surface, roll out the remaining half into a 10 inch square of equal thickness. 
• Freeze on a baking sheet for 15 minutes.
• Do the same thing for the other half.
• Place a 10″ pot lid over each square and cut 2 perfect circles.  Freeze them for another 15 minutes.
• Cover one of the circles with the leek mixture leaving a 3/4″ edge free all around and brush it with cold water.
• Cover the filling with the second circle and press the edges all the way around. 
• Be sure both circles are flush all around the edges.  Prick the edge all around with a fork.
• Refrigerate until needed.

• To cook preheat oven 450°F.
• Decorate the top of the pie by drawing parallel lines 3/4″ apart, then all the way across the previous lines to make a diamond shape figure.
• Brush the glaze over the top and bake for 10 minutes on the middle shelf of the oven.
• Then reduce temperature to 400°F and bake for 30 more minutes. 
• Cover the top with foil toward the end of baking if necessary.
• Remove the pie from the oven and allow to cool for 20 minutes.