Preheat: Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
Make meatballs: In a bowl, mix all meatball ingredients until just combined. Form into 1-1½ inch meatballs and place on a parchment lined baking sheet.
1 lb ground beef, 1 egg, 1/3 cup Italian breadcrumbs, 2 Tbsp. white onion, 2 cloves garlic, 2 Tbsp. milk, 2-3 Tbsp. grated Parmesan cheese, 1 Tbsp. ketchup, 1 Tbsp. Dijon mustard, 1 tsp. Worcestershire sauce, 1 tsp. Italian seasoning, 1 tsp. kosher salt, 1/2 tsp. black pepper
Pre-bake meatballs: Bake at 375°F for ~12-15 minutes (they don’t need to be fully cooked because they’ll finish in the oven). Set aside. Start Timer
Assemble the pasta bake: In the baking dish, add the uncooked pasta, marinara sauce, water or broth, Italian seasoning, and salt. Stir to combine.
12 oz short pasta, 3 cups marinara sauce, 3 cups water or chicken broth, 1 tsp. Italian seasoning, 1/2 tsp. salt
Add meatballs: Carefully add the pre-baked meatballs and gently nestle them into the pasta.
Bake (covered): Cover tightly with foil and bake for 35-40 minutes. Start Timer
Add cheese + finish baking: Remove foil and sprinkle mozzarella + Parmesan over the top. Bake uncovered for another 10-15 minutes Start Timer, until the cheese is melted. I like to broil for the final few minutes until it’s bubbly and lightly golden.
1½ cups shredded mozzarella, ~1/2 cup grated Parmesan
Rest and serve: Allow to rest for a few minutes before diving right in. It's saucy, hot, and it all cooks so perfectly! Garish with fresh parsley and ENJOY!
Garnish: fresh parsley and chili flakes if desired