Preheat your oven to 400°F (200°C).
In a large skillet, cook ground beef or lamb over medium heat until browned. Drain any excess fat.
Add chopped onion and minced garlic to the skillet. Sauté until softened, about 5 minutes.
Stir in tomato paste, beef broth, Worcestershire sauce, and frozen vegetables. Season with salt and pepper. Simmer for 10 minutes.
Spread the beef mixture evenly into a baking dish.
Top with mashed potatoes, spreading them evenly to cover the meat mixture. Use a fork to create a decorative pattern on top.
Bake for 25-30 minutes, or until the top is golden brown and the filling is bubbling.
Let cool for 5 minutes before serving.