From: https://greatlakesgazette.wordpress.com/2012/10/25/recipe-file-mushroom-pie/

Filling

• 2 1/2 cups chopped onions
• 3 tablespoons butter
• 8 cups chopped mushrooms
• 2 teaspoon dried thyme
• 1 teaspoon salt
• lots of freshly ground black pepper
• 8 ounces cream cheese

Preheat oven to 400F.

Add butter to pot, melt and add onions at medium heat. Cook until onions cooked and translucent. Add mushrooms and thime, cook down until liquids cook out. Cut cream cheese into cubes, add to mixture and cook down until thick. Season with salt and pepper to taste.

Crust

• 2 1/2 cups unbleached white flour
• 2 teaspoons baking powder
• 1/4 teaspoon salt
• 1 cup butter
• 1 cup sour cream
• flour for coating the dough and board for rolling

For the crust, combine the flour, baking powder and salt in a large mixing bowl. Cut in the butter just enough to achieve an evenly textured crumbly mix. Stir in the sour cream to form a soft dough. Generously dust the dough with flour and form it into a ball. On a heavily floured board, roll out 2/3 of the dough to fit a 10-inch pie plate. Trim the edges. Fill with the mushroom mixture. Roll out the remaining dough about 1/4 inch thick (thicker than a usual pie crust) and cut into strips. Weave the strips into a lattice over the filling. Fold the ends of the lattice strips under the bottom crust, pinch the edges together, and flute.

Glaze

1 egg 1 tablespoon milk

Cook for 25-35 minutes until crust is soft and golden.