2 pounds potatoes, such as russet, peeled and cubed
2 tablespoons sour cream or softened cream cheese
1 egg yolk
1/2 cup milk
Salt and freshly ground black pepper
1 tablespoon olive oil
1 3/4 pounds ground beef
1 carrot, peeled and chopped
1 onion, chopped
2 tablespoons butter
2 tablespoons all-purpose flour
1 cup beef stock
2 teaspoons Worcestershire
1/2 cup frozen peas
Boil potatoes in salted water until tender, about 12 minutes. Drain potatoes and pour them into a bowl. Combine sour cream, egg yolk and cream. Add the cream mixture into potatoes and mash until potatoes are almost smooth.
While potatoes boil, preheat a large skillet over medium high heat. Add oil to hot pan with beef. Season meat with salt and pepper. Brown and crumble meat for 3 or 4 minutes. Add chopped carrot and onion to the meat. Cook veggies with meat 5 minutes, stirring frequently.
In a second small skillet over medium heat cook butter and flour together 2 minutes. Whisk in broth and Worcestershire sauce. Thicken gravy 1 minute. Add gravy to meat and vegetables. Stir in peas.
Preheat broiler to high. Fill a small rectangular casserole with meat and vegetable mixture. Spoon potatoes over meat evenly. Broil 6 to 8 inches from the heat until potatoes are evenly browned.