In a large skillet, heat the olive oil over medium heat. Add the chopped onion and minced garlic and sauté until translucent, about 4-5 minutes.
Add the ground lamb (or beef) to the skillet, breaking it up with a spatula. Cook until browned, about 6-8 minutes. Drain excess fat if necessary.
Stir in the diced carrots, peas, and corn, cooking for an additional 3-4 minutes until the vegetables are tender.
Mix in the tomato paste, Worcestershire sauce, and beef broth. Season with salt and pepper to taste. Allow to simmer for 5-7 minutes until the mixture thickens slightly.
Transfer the meat and vegetable mixture to a baking dish, spreading it evenly.
Spoon the prepared mashed potatoes over the top of the meat mixture, spreading it out with a spatula to cover completely.
For a golden top, use a fork to create ridges or peaks in the mashed potatoes.
Bake in the preheated oven for 25-30 minutes, or until the top is golden and slightly crisp.
Remove from the oven and allow to cool for a few minutes before serving. Garnish with fresh thyme or rosemary if desired.
Notes
Use beef instead of lamb for a variation. Garnish with fresh herbs for added flavor.