Step 1: Prepare the Panade. In a small bowl, combine the plain breadcrumbs and milk. Let it sit for 5-10 minutes until the breadcrumbs have fully absorbed the milk and softened into a paste.
Step 2: Combine Ingredients. In a large mixing bowl, gently combine the ground beef, ground pork, prepared panade, grated Parmesan cheese, finely minced garlic, chopped fresh parsley, egg, salt, and black pepper.
Step 3: Don't Overmix! Use your hands and mix just until all ingredients are combined. Overmixing will lead to tough meatballs.
Step 4: Form the Meatballs. Using a small ice cream scoop or your hands, form the mixture into approximately 1.5-inch meatballs. You should get about 25-30 meatballs. Place them on a baking sheet lined with parchment paper.
Step 5: Brown the Meatballs. Heat olive oil in a large skillet or Dutch oven over medium-high heat. Once hot, carefully add the meatballs in a single layer, making sure not to overcrowd the pan. Work in batches if necessary.
Step 6: Sear All Sides. Brown the meatballs on all sides, turning occasionally, for about 5-7 minutes total. They don't need to be cooked through at this stage, just nicely seared for flavor and color.
Step 7: Simmer in Sauce. Once browned, carefully transfer the meatballs into a pot of your favorite simmering marinara sauce. Make sure the sauce is gently simmering.
Step 8: Finish Cooking. Cover the pot and let the meatballs simmer in the sauce for at least 30 minutes, or up to an hour, turning them gently occasionally.
Step 9: Serve & Enjoy. Serve hot with your favorite pasta, on a sub roll, or as an appetizer. Garnish with extra fresh parsley and Parmesan cheese if desired.