01 -
Preheat oven to 400°F with a rack in the center position.
02 -
In a large mixing bowl, add diced bread and pour milk or water over it. Soak for 5 minutes and mash with a fork.
03 -
Add ground beef, ground pork, half of the parmesan cheese, egg, minced garlic, chopped parsley, salt, and black pepper to the soaked bread. Mix by hand until just combined. Add more milk if needed, ensuring the mixture stays moist.
04 -
Portion into golf-ball-sized meatballs (about 2 Tbsp per meatball). Wet hands and roll into balls approximately 1 1/2 inches in diameter.
05 -
Heat a large skillet over medium heat and coat the bottom with about 2 Tbsp of oil. Once hot, sear meatballs in batches, turning every 2 minutes to brown evenly. Sear for about 8 minutes total per batch. Meatballs should not be fully cooked through at this stage.
06 -
Spread 1 cup of marinara sauce in a 9x13 casserole dish. Arrange browned meatballs in a single layer over the sauce. Pour remaining marinara sauce over the meatballs and sprinkle with the remaining parmesan and mozzarella cheeses. Cover with foil.
07 -
Bake in the preheated oven for approximately 30 minutes until meatballs reach 165°F internally, the cheese is melted, and the dish is bubbling.