01 - Preheat oven to 400°F. Line a baking sheet with parchment paper and set aside.
02 - In a large mixing bowl, soak breadcrumbs in ¼ cup milk for 5 minutes. Add ground beef, ground pork, onion, garlic, egg, parsley, salt, and black pepper. Mix gently until just combined, being careful not to overwork the meat.
03 - Scoop approximately 2 tablespoons of the meat mixture, flatten it in your palm, and place a mozzarella cube in the center. Wrap the meat around the cheese, shaping into a ball and sealing completely. Repeat with the remaining mixture.
04 - Arrange the stuffed meatballs on the prepared baking sheet. Bake for 20–22 minutes until fully cooked through and golden brown on the outside.
05 - While the meatballs bake, melt butter in a saucepan over medium heat. Whisk in flour and cook for 1–2 minutes, stirring constantly to form a smooth roux.
06 - Gradually whisk in 1 cup milk until smooth and no lumps remain. Continue cooking and stirring for 2–3 minutes until the mixture thickens enough to coat the back of a spoon.
07 - Reduce heat to low. Add grated cheddar, cayenne pepper, smoked paprika, and pickled jalapeños if using. Stir until the cheese has fully melted and the sauce is velvety smooth. Season with salt and pepper to taste.
08 - Serve the hot meatballs drizzled generously with spicy cheese sauce. Garnish with additional chopped parsley if desired. Pair with crusty bread, pasta, or rice.