01 - Preheat oven to 400°F.
02 - Cook potatoes in a large pot of salted boiling water for 15 to 20 minutes until tender. Drain and mash with butter, milk, salt, and pepper. Stir in cheddar cheese if using. Set aside.
03 - Heat olive oil in a large skillet over medium heat. Add onion and carrot, sauté for 4 to 5 minutes until softened.
04 - Add garlic and cook for 1 minute until fragrant.
05 - Add ground beef or lamb, breaking up with a spoon, and cook until browned. Drain excess fat if needed.
06 - Stir in tomato paste, Worcestershire sauce, thyme, salt, and pepper.
07 - Add broth and peas. Simmer for 5 minutes until slightly thickened. Remove from heat.
08 - Divide meat filling evenly among six lightly greased ramekins or muffin tin wells.
09 - Spoon or pipe mashed potatoes on top of each, spreading to cover the filling completely.
10 - Place ramekins on a baking sheet and bake for 20 minutes until tops are golden and filling bubbles at edges.
11 - Cool for 5 minutes before serving.