A traditional recipe is a perennial favorite. You can substitute items, depending upon what you have in the fridge at the time! You can use pork or chicken instead of beef.
Preheat oven to 375 F. Place ground beef, mushrooms, onion, garlic, salt, and pepper in a large heavy skillet. Sauté until the juices have almost evaporated. Stir in Worcestershire sauce, then cook for one minute, stirring often. Add beef stock, stirring to combine, then add cream. Simmer until gravy thickens. Pour into glass baking dish. Let cool slightly, then sprinkle green peas evenly on top of beef.
Boil potatoes in salted water until tender. Add 2 tablespoons of butter, and mash. Add enough milk to bring the mashed potatoes to a creamy consistency. Season well with salt and pepper. Spread evenly over beef layer then sprinkle Cheddar cheese on top.
Bake for about 45 minutes until cheese has melted and is slightly browned.