In a large mixing bowl, tear the white bread into small pieces and pour in the milk or cold water. Allow this mixture to soak for about 5 minutes until the bread absorbs the liquid and softens. Then, mash it with a fork or your hands into a smooth paste, creating the panade.

Once the panade is ready, add the ground beef, ground pork, Parmesan cheese, egg, minced garlic, chopped parsley, sea salt, and black pepper to the bowl. Gently mix these ingredients by hand until just combined; be careful not to overmix.

With wet hands, take a portion of the meat mixture and roll it into a ball about 1½ inches in diameter. Place the formed meatballs on a lined baking sheet, ensuring they are spaced about an inch apart.

Heat the olive oil in a non-stick skillet over medium heat until shimmering. Carefully add the meatballs to the skillet in batches, sautéing them for 6–8 minutes until browned on all sides and reaching an internal temperature of 160°F.

Preheat your oven to 400°F. Arrange the meatballs on a baking sheet lined with parchment paper, keeping them at least 2 inches apart. Bake for 20–23 minutes, or until golden brown.

If using a slow cooker, first brown the meatballs in a skillet, then transfer them to the slow cooker and cover them with marinara sauce. Cook on low heat for about 6 hours.