A shepherd's pie recipe at CampbellsKitchen.com uses frozen vegetables and instant mashed potatoes to make minimize preparation time. Martha Stewart's shepherd's pie also uses frozen vegetables and you can prepare it a day in advance.
Start the Campbell's shepherd's pie by browning 1 pound of ground beef with 1/2 cup chopped onion in a 10-inch skillet over medium-high heat. Drain the fat. Stir 1 can Campbell's Condensed Cream of Mushroom Soup, 1 tablespoon ketchup, 1/8 teaspoon ground black pepper and 1 cup frozen peas and carrots into the skillet. Spoon the mixture into a 9-inch pie plate. In a saucepan over medium-high heat, bring 2 1/2 cups reduced-fat milk and 1/4 cup (1/2 stick) butter to a boil. Remove the pan from the heat, and stir in 2 cups instant mashed potato flakes or buds to make stiff mashed potatoes. Spread the potatoes evenly over the beef mixture. Bake at 400 F for 15 minutes until lightly browned.
To make Martha Stewart's recipe, brown 1 pound of ground chuck. Add 1 medium chopped onion and 1 minced garlic clove and cook until softened. Stir in 1/4 teaspoon dried thyme, 2 tablespoons ketchup and 1 tablespoon flour. Add 1/2 cup water and 10 ounces of frozen mixed vegetables. Cook until the vegetables are warm and the sauce thickens, approximately three minutes. Season with salt and pepper. Spoon the beef mixture into a 2-quart baking dish. Spread 3 cups of mashed potatoes on top. Place the dish on a baking sheet and cook for 10 to 15 minutes at 425 F until the potatoes are lightly browned.