In a large mixing bowl, stir together bread crumbs and milk, adding more milk 1 Tbsp at a time to moisten bread fully. Let rest while you prep ingredients (or at least 5 minutes).

To the breadcrumb mixture, add beef, pork, eggs, onion, garlic, basil, parsley, oregano, and Parmesan. Season evenly over the top of the ingredients with salt and pepper.

Gently toss the mixture and break up the meat with your fingertips until the ingredients are evenly mixed.

Shape the mixture with greased hands into even-sized meatballs, about 1.25 inches each.

Preheat oven to 400°F (200°C).

Spray two dark-coated non-stick baking sheets well with non-stick cooking spray, or brush with olive oil.

Place formed meatballs on the baking sheets, fitting about 20 per sheet and spacing evenly apart. Bake in the upper and lower thirds of the oven for 10 minutes.

Remove from oven and turn the meatballs if browned on the bottom. Transfer pans to opposite racks and bake until cooked through, about 8-12 minutes longer (should register 165°F/74°C in the center of the meatballs).

Stir into warmed marinara sauce. Simmer on low heat if desired for even more tender meatballs (about 10-20 minutes, tossing gently occasionally).

To pan-fry meatballs, pour 0.75 cup olive oil into a 12-inch non-stick skillet and heat over medium heat.

Cook meatballs in 3 batches (to avoid overcrowding) until golden brown on the bottom, about 4-6 minutes. Then, turn to the opposite side and cook until golden brown. Transfer to paper towels to drain.

Transfer meatballs to warmed marinara sauce in a large pot, submerging them in the sauce. Cover and simmer over low heat until meatballs reach 165°F (74°C) in the center, gently tossing occasionally, about 15-20 minutes.