1. Preheat your oven to 375°F (190°C).
2. In a large mixing bowl, combine ground beef (or turkey), breadcrumbs, eggs, Worcestershire sauce, chopped onion, garlic powder, salt, and pepper. Mix well until all ingredients are evenly incorporated.
3. Grease a standard 12-cup muffin tin lightly with oil or cooking spray.
4. Divide the meat mixture evenly among the muffin cups, pressing it down firmly to fill each cup.
5. Place the muffin tin in the preheated oven and bake for 15 minutes.
6. While the meatloaf is baking, mix together ketchup, maple syrup, nutmeg, and Dijon mustard in a small bowl to make the sauce.
7. After 15 minutes, remove the meatloaf muffins from the oven.
8. Carefully blot out any excess grease from the muffin cups if necessary.
9. Spoon the prepared sauce evenly over each meatloaf muffin.
10. Return the muffin tin to the oven and bake for an additional 10-15 minutes, or until the meatloaf muffins are cooked through and the sauce is caramelized.
11. Once cooked, allow the mini meatloaf muffins to cool slightly before serving. Enjoy them hot with your favorite sides!