Preheat the oven to 375 degrees Fahrenheit and grease a standard 12-cup muffin tin.

Heat the olive oil in a skillet over medium heat, sauté the onion for about 5 minutes until softened, then add the garlic and cook for 1 additional minute before allowing the mixture to cool slightly.

In a large bowl, combine the ground beef, eggs, breadcrumbs, milk, Parmesan cheese, onion mixture, salt, pepper, Worcestershire sauce, and ketchup, then mix until just combined.

Divide the meat mixture evenly among the prepared muffin cups, filling each generously and gently pressing the mixture into the cups.

Bake for 15 minutes.

While the meatloaf muffins bake, whisk together the ketchup, mustard, and brown sugar in a small bowl until smooth.

Remove the muffin tin from the oven, spoon the glaze evenly over the tops, and return to the oven for an additional 10-15 minutes or until the centers reach 160 degrees Fahrenheit.

Let the meatloaf muffins rest for 5 minutes before removing from the pan and serving warm.