01 - Preheat oven to 400°F. Lightly grease a 9x13 inch baking dish with cooking spray or oil.
02 - In a large bowl, combine ground beef, breadcrumbs, Parmesan cheese, egg, minced garlic, chopped parsley, milk, oregano, salt, and pepper. Mix gently until just combined—avoid overworking to keep meatballs tender.
03 - Roll mixture into 24 small meatballs, using approximately 1 tablespoon of mixture per meatball.
04 - Heat olive oil in a large skillet over medium-high heat. Add meatballs and brown on all sides for about 5 minutes. Remove from skillet and transfer to a plate—meatballs will finish cooking in the oven.
05 - Bring a large pot of salted water to boil. Cook pasta for 2 minutes less than package directions to achieve al dente texture. Drain well in a colander.
06 - In the prepared baking dish, combine the partially cooked pasta, marinara sauce, and water. Stir thoroughly to ensure pasta is evenly coated with sauce.
07 - Nestle browned meatballs evenly throughout the pasta. Sprinkle shredded mozzarella and grated Parmesan cheese generously over the entire surface.
08 - Cover baking dish tightly with aluminum foil. Bake for 25 minutes to allow flavors to meld and pasta to finish cooking.
09 - Remove foil and continue baking for 15–20 minutes, or until cheese is golden brown and sauce is bubbling around the edges.
10 - Let the casserole rest for 10 minutes before serving to allow flavors to set and make serving easier. Garnish with torn fresh basil leaves.