01 - Preheat the oven to 400°F.
02 - Place sweet potatoes in a large pot, cover with salted water, and bring to a boil. Simmer for 15–20 minutes until tender. Drain well.
03 - Mash sweet potatoes with milk, butter, salt, and pepper until smooth. Set aside.
04 - Heat olive oil in a large skillet over medium heat. Add onion and cook for 3 minutes until translucent. Add garlic and carrots; cook for 4–5 minutes, stirring occasionally.
05 - Add ground beef and cook until browned, breaking up with a spoon, about 5 minutes. Drain excess fat if needed.
06 - Stir in tomato paste, beef stock, Worcestershire sauce, dried thyme, salt, and pepper. Simmer for 8–10 minutes until slightly thickened.
07 - Stir in frozen peas and cook for 2 more minutes. Adjust seasoning as needed.
08 - Transfer beef mixture to a 2-quart baking dish. Spread sweet potato mash evenly over the top, using a fork to create ridges.
09 - Bake for 20 minutes, or until the mash is lightly golden. For extra browning, broil for 2–3 minutes at the end.
10 - Rest for 5 minutes before serving.