Preheat your oven to 350 degrees Fahrenheit.
Place bread slices in a large bowl. Cover with milk and allow to soak.
In a large skillet melt 1 tablespoon butter. Cook onions until tender. Add in garlic and cook a minute or two longer. Remove from heat.
In a large bowl, combine ground beef, bread mixture, onion mixture, salt, black pepper, and fresh parsley. Add in 2 eggs, slightly beaten. Stir in 1 tablespoon Worcestershire sauce. Mix until everything is well combined. I like to use clean hands for this job, it is much easier than trying to use a large spoon.
Prepare a rimmed baking sheet by covering it with parchment paper.
Pour the meat mixture onto the prepared pan and use your hands to shape it into a loaf.
In a small bowl combine the sauce ingredients: 1 cup ketchup with 1/4 cup brown sugar and 3 tablespoons mustard. Pour half the sauce over the meatloaf.
Bake for 40 minutes, then top with remaining sauce and continue baking for another 20 minutes, or until the internal temperature of the meatloaf reaches 160 degrees Fahrenheit.