01 - Preheat the oven to 400°F.
02 - Place peeled and cubed sweet potatoes in a large pot, cover with cold water, add a pinch of salt, bring to a boil, and simmer for 15-20 minutes until tender.
03 - Drain sweet potatoes and mash with butter, milk, salt, and pepper until smooth. Set aside.
04 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook 2-3 minutes until softened.
05 - Add minced garlic and diced carrots to the skillet and cook for 3 minutes.
06 - Add ground beef, breaking it up with a spoon, and cook until browned, about 5-7 minutes.
07 - Stir in tomato paste, Worcestershire sauce, dried thyme, and rosemary. Cook for 2 minutes.
08 - Pour in beef broth, bring to a simmer, and cook for 5 minutes until slightly thickened.
09 - Stir in frozen peas and season with salt and pepper. Remove from heat.
10 - Spoon beef filling into a 2 quart baking dish and spread sweet potato mash evenly on top.
11 - Use a fork to create ridges on the sweet potato mash surface for crispiness.
12 - Bake for 20-25 minutes until the top is golden and the filling is bubbling.
13 - Let stand for 5 minutes before serving.