In a large mixing bowl, combine ground beef, minced garlic, breadcrumbs, a large egg, ketchup, yellow mustard, Worcestershire sauce, salt, black pepper, and fresh parsley. Mix gently until just combined.

Using wet hands, scoop a portion of the mixture and roll it into balls about 1.5 inches in diameter. Aim for 24 to 26 meatballs.

Heat olive oil in a large skillet over medium-high heat. Add the meatballs in batches, cooking for about 2 minutes on each side until golden brown.

In the same skillet, lower heat and add unsalted butter and diced onion. Cook for about 15 minutes until onions are caramelized.

Add chicken broth, beef broth, beef bouillon cube, onion powder, garlic powder, Worcestershire sauce, and smoked paprika to the skillet. Bring to a gentle boil.

Mix cornstarch with water to create a slurry. Slowly pour this mixture into the bubbling gravy while stirring to prevent lumps.

Add browned meatballs back into the skillet, ensuring they're submerged in the gravy. Let them simmer for about 10 minutes.

Remove from heat and let the dish rest for a few minutes before serving.