Position a rack in the center of the oven; preheat to 475 degrees .
Preheat a large cast-iron skillet over medium-high.
In a medium bowl, mix the breadcrumbs and milk to moisten. Add the ground meat, pancetta, 1/3 cup of each cheese, 2 tbsp. EVOO, two turns of the bowl, the egg, parsley, chopped garlic, onion flakes, oregano, fennel pollen and crushed red pepper; season with salt and pepper and gently mix to blend. Roll the mixture into 2- to 2 1/2-inch meatballs and drizzle with a little more EVOO.
Add the remaining 2 tbsp. EVOO to the skillet, two turns of the pan; melt in the butter. Add the crushed garlic and stir until aromatic, about 1 minute. Add the wine and cook, stirring often, until slightly reduced, about 2 minutes. Add the stock and the tomatoes and their juices, crushing the tomatoes with your hands as you add them. Season with salt; add the basil, stirring to wilt. Set the meatballs into the sauce but do not cover (tops should be exposed). Roast until the meat is just cooked through and the tops are browned, 15 to 18 minutes.
Serve meatballs from the skillet with crusty bread for mopping and extra cheese for topping.