In a large skillet over medium heat, add the ground lamb or beef. Cook until browned, breaking it apart with a spatula, about 5-7 minutes. Drain any excess fat.
Add diced onion and minced garlic to the skillet. Sauté until the onion becomes translucent, about 3 minutes.
Stir in the mixed vegetables and cook for another 3-4 minutes until they are slightly tender.
Add the tomato paste, broth, Worcestershire sauce, thyme, salt, and pepper to the skillet. Bring to a simmer and cook for 5 minutes, allowing the flavors to meld.
Transfer the meat and vegetable mixture to a baking dish, spreading it out evenly.
Spoon the mashed potatoes over the meat mixture, spreading them with a spatula to cover completely. Create decorative peaks if desired.
If using cheese, sprinkle it on top of the mashed potatoes.
Bake in the preheated oven for 25-30 minutes or until the top is golden brown and bubbly.
Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley if desired before serving.
Notes
Feel free to use store-bought mashed potatoes for a quicker option.
Keyword beef, comfort food, lamb, mashed potatoes, shepherd's pie