Preheat your oven to 375°F (190°C).
In a large skillet over medium heat, cook the ground beef until browned. Drain excess fat.
Add the chopped onion and minced garlic to the skillet, cooking until the onion is translucent.
Stir in the ketchup, Worcestershire sauce, brown sugar, mustard, chili powder, salt, and pepper. Simmer for about 5 minutes until thickened.
While the mixture simmers, slice the French bread in half lengthwise.
In a small bowl, mix the softened butter with garlic powder. Spread the garlic butter evenly on both halves of the bread.
Spoon the Sloppy Joe mixture generously over the garlic buttered bread.
Sprinkle the cheddar and mozzarella cheeses evenly on top of the Sloppy Joe mixture.
Place the bread on a baking sheet and bake for 15-20 minutes, or until the cheese is melted and bubbly.
Remove from the oven, garnish with fresh parsley if desired, slice, and serve warm.