Preheat the oven to 400°F. Lightly spray a 9-inch deep dish pie pan or similar sized baking dish with nonstick cooking spray.
In a large skillet, heat the butter over medium high heat. Sauté the garlic and leeks for 5 minutes, until tender. Add the carrots, mushrooms, and rosemary, season with salt and pepper, and sauté for about 8 minutes, until the mushrooms are turning brown (they may release liquid as they begin to cook; keep sautéing the vegetable mixture until the liquid has evaporated and the vegetables start to caramelize.) Then stir in the flour, and continue to stir and cook for another 2 minutes until the flour gets a bit toasted. Add the Campbell’s Condensed Cream of Mushroom Soup and water, stir, and bring to a simmer. Simmer for about 3 minutes until the mixture has thickened a bit. Add the peas, pearl onions and chicken, and return the mixture to a simmer. Stir in the parsley.
Turn the mixture into the pie pan. Roll out the puff pastry dough slightly on a lightly floured surface.
Place the puff pastry over the filling, and trim off the corners if they hang below the bottom of the pan. Brush the top of the pastry with the beaten egg and use a sharp knife to make several slits in the crust so steam can escape. Bake for 20 to 30 minutes until the crust is golden brown and everything is bubbly.
Notes
What the Kids Can Do:
Peel carrots, slice mushrooms, measure ingredients, shred chicken, roll the puff pastry, place it on the pie, and cut slits in it.