Step 1: Prepare the Mashed Potatoes

Boil the potatoes in salted water for 15–20 minutes or until fork tender. Drain and return to the pot. Add butter, milk, sour cream, salt, and pepper. Mash until smooth and creamy. Set aside.

Step 2: Cook the Meat Filling

In a large skillet, heat olive oil over medium heat. Add chopped onion and cook until soft. Stir in garlic, carrots, and cook for 5 minutes. Add ground lamb or beef, cooking until browned and crumbled.

Step 3: Add Flavor and Simmer

Stir in tomato paste, Worcestershire sauce, rosemary, thyme, and flour. Mix well. Add broth and bring to a simmer. Cook uncovered for 10–12 minutes until the mixture thickens. Add frozen peas and cook for 2–3 minutes more. Taste and adjust seasoning.

Step 4: Assemble the Pie

Preheat oven to 400°F (200°C). Spread the meat mixture evenly into a baking dish. Gently layer the mashed potatoes over the top using a spatula. For a decorative look, use a fork to create ridges. Sprinkle with shredded cheddar cheese if desired.

Step 5: Bake and Serve

Bake uncovered for 20–25 minutes or until the top is golden brown and slightly crisp. Let rest for 5–10 minutes before serving.