1. Preheat oven to 375.

For the Crust

1. Mix flour, salt, pepper, Parmesan cheese and baking powder in food processor bowl with a metal blade attachment. Add diced butter and cream cheese and loosely mix to coat the pieces. Pulse the mixture until the crumbs are about the size of peas . Add ice water and process only enough to moisten the dough and have it start forming . (This can also be done with a pastry blender - just break butter and cream into pea sized chunks in the flour mixture. Add water and mix with a wooden spoon until it forms a ball.)
2. Dump dough onto a floured surface and quickly shape into a ball. Wrap dough in plastic wrap and put in fridge to rest for 30 minutes.

For the Filling

1. Cook and dice chicken. Set aside.
2. In deep skillet, melt the butter and sauté the mushrooms and onions over medium-low heat about 10 minutes, until translucent and browning. Turn heat to medium-low. Add flour to make your roux – stirring constantly to prevent lumping. Once well incorporated, add hot chicken stock to mixture, stir to prevent lumping. Once all stock is added, simmer over low for an additional 1-2 minutes, or until thick. Add cream or milk, salt, and pepper to taste. Add chicken, carrots, peas and parsley. Mix until well incorporated.

Assembly:

1. Put filling into 9x13 deep dish pan or 2 pie pans.
2. Get dough out of fridge and roll on a floured surface into a rectangle slightly larger than the pan. Brush the outside edges of the pan with egg wash. Place the dough on top and trim the excess, pressing the edges to the inside of the pan. Tip: if there is a thin spot of dough, or a corner that’s not quite to the edge, take your trimmings and fill in where needed.
3. Generously brush dough with egg wash (this miraculously makes the dough kind of all “melt” together so you can’t even tell where the patchwork was).
4. Make a few slits in the top of the dough. Place on baking sheet and bake for 1 hour, or until golden brown with hot filling.