Peel and quarter 2 pounds of russet potatoes, then place them in a large pot of salted water. Bring to a boil and cook for 15-20 minutes until fork-tender.

Drain the potatoes and mash with ½ cup warm milk, 4 tablespoons butter, and salt until creamy.

In a large skillet, heat 1 tablespoon of oil over medium-high heat. Add 1 pound of ground beef or lamb and cook for about 5-7 minutes until browned.

To the browned meat, stir in 1 diced onion, 2 minced garlic cloves, and 2 chopped carrots. Cook for 5-7 minutes until softened.

Add 1 cup of frozen peas and cook for an additional 2 minutes.

Sprinkle 2 tablespoons of flour over the filling, stirring for 1 minute. Gradually add 1 cup of beef broth and 2 tablespoons of tomato paste, cooking until thickened.

Add 1 teaspoon of Worcestershire sauce, ½ teaspoon of dried thyme, and black pepper to taste.

Transfer the meat mixture to a greased 9x13-inch baking dish. Top with the mashed potatoes, creating peaks.

Preheat your oven to 400°F (200°C). Bake for 20-25 minutes until bubbly and golden brown.

Broil for an additional 2-3 minutes for a crispier topping.

Let rest for 5-10 minutes before serving.