Preheat your oven to 375°F (190°C). Lightly grease a 12-cup muffin tin or line it with paper baking liners.
In a small bowl, pour the milk over the breadcrumbs and allow them to soak for 5 minutes, softening into a paste-like consistency.
In a separate large mixing bowl, combine the ground meat, soaked breadcrumb mixture, egg, grated onion, minced garlic, Worcestershire sauce, Italian seasoning, salt, pepper, smoked paprika (if using), and Parmesan cheese. Using your hands, gently blend everything together until just incorporated—take care not to overmix.
Spoon approximately 2 tablespoons of the meat blend into each muffin cup. Press down slightly and use your thumb or a spoon to form a shallow indentation in the center.
Drop a heaping tablespoon of shredded cheese into each well, then add another spoonful of the meat mixture on top, carefully sealing the cheese within.
In a small dish, combine the ketchup, brown sugar, and mustard until smooth. Spoon a small amount of this glaze over each meatloaf portion.
Transfer the muffin tin to the oven and bake for 20 to 25 minutes, or until the internal temperature of the meat reaches 160°F (71°C).
Allow the bites to sit for 5 minutes after baking before gently removing them from the muffin tin. Serve warm, accompanied by extra ketchup or alongside mashed potatoes if desired.