Chicken Pot Pie

1 sheet frozen puff pastry, thawed
2 cups milk
1 stick unsalted butter
3 cups chicken stock
1 large onion
1 cup frozen peas (optional)
4 large potatoes
2 tablespoons thyme leaves
1 ½ cup chopped carrots
5 teaspoons salt
12 ounces sliced mushrooms
2 teaspoons ground pepper
1 cup cooking sherry
2 tablespoons parsley
8 tablespoons flour
1 large egg
4-5 large chicken breasts, poached and diced

Preheat oven to 425 degrees. Remove puff pastry from freezer and allow to thaw. Melt butter in a very large pot over medium high heat. Add onion, potatoes and carrots. Cook, stirring occasionally, until the potatoes and carrots are fork tender, 15-20 minutes.

Add mushrooms, cooking until mushrooms are heated through. Add sherry and cook for 3 minutes. Add flour and cook, stirring for 1 minute. Pour in chicken stock and milk. Bring to a simmer, cook until thick and bubbly, stirring constantly. Stir in chicken , peas, parsley and thyme. Season with salt and pepper. Transfer amount needed to a deep 3-quart dish. Set aside the rest and let cool before freezing.

Roll out puff pastry and cut 1 inch larger then dish. Cut out quarter-size whole in the center. Place puff pastry on filling, making sure it touches the filling all the way to the sides of the dish. Fold over any excess. Whisk egg with ½ teaspoon water, and brush top of pastry, making sure to cover completely.

Place dish in over and bake for 20-30 minutes, until crust is well browned.

For frozen filling: Let filling completely defrost. Place in dish and follow same steps to make crust. The puff pastry sheets come 2 to a pack, so you should have one left over. Cook until crust is browned, 20-30 minutes. Cover loosely with tin foil and cook another 5-10 minutes until filling is hot.