Peel and cube the sweet potatoes, then boil in salted water until tender, about 15 minutes.
While potatoes boil, heat avocado oil in a large oven-safe skillet over medium heat and sauté diced onion until translucent.
Add the ground beef to the skillet, breaking it apart with a spoon, and cook until browned through.
Stir in the minced garlic, tomato paste, sea salt, black pepper, and dried thyme, cooking for 1 minute until fragrant.
Pour in the beef bone broth and frozen peas, simmering for 5 minutes until the liquid reduces slightly.
Drain the sweet potatoes and mash them with ghee until smooth and creamy.
Spread the mashed sweet potatoes evenly over the beef mixture in the skillet.
Place the skillet under the broiler for 3-5 minutes until the potato topping is lightly crisped and golden.