Preheat the oven: Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper or lightly grease it.

Prepare the meatball mixture: In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, eggs, minced garlic, parsley, salt, black pepper, oregano, basil, onion powder, and red pepper flakes. Add the milk and mix everything together until well combined. The mixture should be moist but firm.

Shape the meatballs: Using your hands, form the meat mixture into 1 to 1.5-inch meatballs and place them on the prepared baking sheet. You should have around 20 meatballs.

Cook the meatballs: In a large skillet, heat the olive oil over medium heat. Working in batches, brown the meatballs on all sides, about 3-4 minutes per batch. Once browned, transfer the meatballs to a plate.

Simmer the meatballs in sauce: In the same skillet, add the marinara sauce, beef broth, and a tablespoon of olive oil. Stir in garlic powder, red pepper flakes (if using), and salt and pepper to taste. Bring the sauce to a simmer, then carefully add the browned meatballs to the sauce.

Cook the meatballs in the sauce: Cover the skillet with a lid and simmer the meatballs in the sauce for 15-20 minutes, or until they are cooked through and the sauce has thickened slightly.

Serve: Serve the Mountain Meatballs hot, either on a bed of pasta, in sub rolls for meatball sandwiches, or on their own with a side of garlic bread. Garnish with extra parsley and Parmesan cheese, if desired.