In a large mixing bowl, combine the ground beef, ground pork, fresh breadcrumbs, grated Parmesan, shredded mozzarella, eggs, minced garlic, finely chopped onion, chopped parsley, dried oregano, salt, pepper, and whole milk. Mix gently until just combined.

Wet your hands lightly and form the mixture into golf ball-sized portions, aiming for approximately 24 meatballs, and place them on a parchment-lined baking sheet.

Heat olive oil in a large skillet over medium heat. Add the meatballs and brown them for 2-3 minutes on each side until golden.

In the same skillet, sauté minced garlic in olive oil over medium heat for about 1 minute until fragrant.

Add canned crushed tomatoes, dried basil, dried oregano, red pepper flakes, sugar, salt, and pepper to the skillet. Stir to combine and bring to a gentle simmer for about 5 minutes.

Nestle the browned meatballs into the simmering marinara sauce, cover, and let simmer on low heat for 20-25 minutes.

Garnish with fresh basil leaves and serve over pasta or with crusty bread.