Preheat oven to 400F with a rack in the center of the oven. In a large mixing bowl, add diced bread. Pour milk/water over the bread and soak for 5 minutes then mash with a fork.

Add ground beef and pork, half of the parmesan cheese, egg, minced garlic, chopped parsley, salt and black pepper. Use your hands to stir until just combined. Do not over-mix. The mixture should feel very moist. If not, add a bit more milk as needed.

Portion into golf-ball-sized meatballs, about 2 Tbsp per meatball. A trigger release scoop makes it easy to portion. Wet your hands and roll into meatballs about 1 ½” in diameter.

Set a large skillet over medium heat and coat the bottom with oil, about 2 Tbsp. Once the oil is hot, add the meatballs to the skillet in batches and turn every 2 minutes to get a good sear on all sides. Each batch will cook for about 8 minutes in total. They don’t need to be fully cooked through at this point, just browned all over.

Add 1 cup marinara to a 9x13 casserole dish. Arrange the browned meatballs over the sauce in a single layer. Pour the remaining marinara over the top and sprinkle with the remaining parmesan cheese and mozzarella cheese.* Cover with foil and bake until the meatballs are cooked through to 165 ̊F on an instant-read thermometer, the cheese should be melted and the casserole should be bubbling, about 30 minutes.