Preheat and prep: Heat your oven to 425°F (220°C). Line a sheet pan with foil and set a wire rack on top, if you have one. Lightly oil the rack so the meatballs don’t stick.

Make a panade: In a large bowl, stir the breadcrumbs and milk together. Let it sit 2–3 minutes until the crumbs absorb the milk. This step keeps the meatballs soft and tender.

Add aromatics: Mix in the grated onion, garlic, parsley, oregano, red pepper flakes (if using), 1 teaspoon kosher salt, and 1/2 teaspoon black pepper.

Fold in cheese and eggs: Add the Parmesan and the eggs to the bowl. Stir until evenly combined. You should have a thick, cohesive mixture.

Add the meats: Add the ground beef and ground pork. Use your hands to gently mix, folding the mixture from the outside in. Do not overwork or the meatballs will get tough. Stop as soon as everything looks evenly distributed.

Shape the meatballs: Lightly oil your hands. Roll into golf ball–size meatballs (about 1.5 inches). You should get 18–22 meatballs, depending on size. Place them on the prepared rack or sheet pan.

Choose your cooking method: Oven-baked: Drizzle or mist with olive oil. Bake 15–18 minutes, until lightly browned and the centers reach 165°F (74°C).

Pan-seared + simmered: Heat 2 tablespoons olive oil in a wide skillet over medium-high. Sear meatballs in batches, turning to brown all sides (6–8 minutes total). Add marinara and simmer on low 10–15 minutes until cooked through.

Finish and serve: Taste a small piece for seasoning. Add a squeeze of lemon for brightness if you like. Sprinkle more Parmesan and chopped parsley on top. Serve with spaghetti, crusty bread, or over polenta.