Preheat oven to 350°F. Line a rimmed sheet pan with foil and lightly oil it.
Warm olive oil in a skillet over medium heat. Soften onion 4–5 minutes. Stir in garlic for 30 seconds. Cool.
Soak breadcrumbs in milk in a large bowl for 5 minutes to form a panade.
Whisk beaten eggs with Worcestershire, 2 tbsp ketchup, tomato paste, Parmesan, parsley, Italian seasoning, salt, pepper, and flakes.
Add cooled onions to the bowl. Stir the mixture until evenly combined.
Add ground beef and pork. Mix gently with your hands just until combined; do not overwork.
Fold in 1 cup mozzarella, reserving the rest for topping.
Shape into a 9×4-inch loaf on the pan. Blend marinara with remaining 1 tbsp ketchup and brush over the top.
Bake 45 minutes. Sprinkle remaining mozzarella over the loaf and bake 8–10 minutes more, until cheese browns and center hits 160°F.
Rest 10 minutes before slicing. Serve warm with extra marinara if you like.
Notes
Variation: Swap half the mozzarella for provolone or fontina. For a spicier loaf, add 1–2 tsp Calabrian chile paste to the glaze. Storage: Refrigerate slices up to 4 days or freeze up to 2 months; reheat covered at 325°F until hot.This recipe is an original creation inspired by classic Savory Italian Meatloaf with Cheese flavors. All ingredient ratios and instructions are independently developed.