In a large skillet over medium heat, cook ground beef until browned. Add diced onion and minced garlic. Sauté until the onions are soft. Stir in diced carrots and cook for 5 minutes.

Mix in tomato paste and Worcestershire sauce. Sprinkle in flour and stir until absorbed.

Pour in beef broth and stir until thickened. Add frozen peas. Simmer for 2 minutes. Season with salt and pepper to taste.

While the meat mixture simmers, boil peeled and cubed potatoes until fork-tender (about 15 minutes). Drain and mash with butter and milk. Add salt and pepper to taste.

Preheat oven to 400°F. Transfer beef mixture to a baking dish. Spread mashed potatoes evenly on top. Use a fork to create texture on the surface. Bake for 25 minutes, or until the top is golden.