Beef Pie with Stout (Skillet)

A store-bought crust makes this one-pan beef pie even easier, and the hearty filling is sure to make for a family favourite.
1 Tbsp. olive oil
1 lb lean ground beef
4 oz small shiitake mushrooms
sea salt
black pepper, freshly ground
2 Tbsp. tomato paste
½ cup frozen pearl onions
1 Tbsp. fresh thyme leaves
3 Tbsp. all-purpose flour, unbleached
8 oz stout (we used Guinness)
2 cups frozen butternut squash pieces
1 cup frozen peas
1 refrigerated rolled pie crust
1 large egg
Preheat oven to 375°F (190°C, Gas Mark 5).
Heat the oil in a 9" cast-iron skillet over medium heat. Add the beef, mushrooms and ¾ tsp. each salt and pepper, and cook, breaking up the beef with a spoon, until browned, 4-6 minutes. Spoon off and discard any fat.
Add the tomato paste and cook, stirring, for 2 minutes. Stir in the onions and thyme, then sprinkle with the flour and cook, stirring, for 30 seconds.
Add the stout and simmer until the liquid has thickened, about 1 minute. Add ½ cup water and bring to a simmer. Add the squash and peas, return to a simmer, then remove from heat. (This whole step takes only 2-3 minutes total.)
Unroll the pastry on a cutting board, brush with the egg, then cut a cross in the center. Lay the dough on top of the beef mixture (egg-side up), gently pressing the edges around the inside of the skillet. Bake until golden brown, 30-35 minutes. Let rest for 5 minutes before serving.
Makes 4 servings.