Brown onions and meat in a large frying or sauce pan over medium heat, stirring
frequently.
Add remaining ingredients and simmer for 15 minutes, stirring.
Place thin potato slices on the bottom pie crust, spiral fashion.
Pour meat mixture into bottom crust. Top with another pastry crust.
Slit steam holes in the top of the crust.
Brush with egg yolk with a little water. With a pastry brush, glaze the top of the crust.
Bake in a preheated 400 degree oven for 40 minutes or until top is nicely browned.
Let cool slightly and serve!