Chop Mixed Vegetables (2 cup) and Vegan Meat (1 cup) into bite-sized or smaller pieces.
Layer vegetables and chopped holiday roast into a 5-inch by 7-inch casserole dish.
Top with Mushroom Gravy (1 1/2 cup), ensuring all vegetables and roast are well coated.
Spoon Mashed Potatoes (2 1/2 cup) over the top of the base, starting with the edges to form a seal and working inwards.
Place casserole dish on a baking sheet or layer of aluminum foil to prevent a messy cleanup if the filling boils over.
Bake for 35 minutes, or until the gravy is bubbling and the mashed potatoes are slightly browned and crisp on top. If necessary, brown the mashed potato topping under the broiler for a couple of minutes.