Preheat your oven to 400°F (200°C).

In a large skillet over medium heat, brown the ground lamb, breaking it up with a spoon until it’s no longer pink. Transfer to a plate and drain off any excess fat.

In the same skillet, add the chopped onion and diced carrots, stirring frequently until the onion is translucent, about 5 minutes.

Add the minced garlic and cook for an additional minute.

Stir in the cooked lamb, tomato paste, Worcestershire sauce, dried thyme, salt, and pepper. Cook for another minute.

Add the stock and bring it to a simmer, letting it thicken slightly, about 5 minutes.

Fold in the frozen peas and mix well.

Boil the diced potatoes in salted water until fork-tender, about 15-20 minutes.

Drain well and return to the pot, mashing until smooth and creamy.

Stir in milk, butter, and season with salt and pepper to taste. If desired, add a dash of nutmeg.

In a baking dish, pour in the meat and veggie mixture, spreading it out evenly.

Dollop and spread the mashed potatoes on top.

Create swirls and peaks with a fork.

Bake in the preheated oven for 25-30 minutes, until the top is golden brown.

Let it rest for a few minutes before serving.