Peel and cube sweet potatoes, boil until fork-tender (15-20 minutes). Drain and mash with milk, melted butter, cinnamon, nutmeg, ginger, salt, and pepper.
In a skillet, brown ground beef over medium-high heat; drain excess grease.
Add chopped onion and minced garlic; sauté until softened.
Stir in chopped green bell pepper, canned tomatoes (with juice), tomato sauce, oregano, basil, salt, pepper, and Worcestershire sauce; simmer.
Preheat oven to 375°F (190°C). Layer meat mixture in a greased baking dish, top with mashed sweet potatoes and shredded cheese.
Bake for 20–25 minutes until bubbly. Let rest before serving.