01 - Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
02 - Cook the elbow macaroni according to package directions until al dente. Drain thoroughly and set aside.
03 - In a medium saucepan over medium heat, melt the unsalted butter. Whisk in the all-purpose flour and cook for 1 minute, creating a roux. Gradually whisk in the whole milk, stirring continuously until the mixture thickens, approximately 2-3 minutes.
04 - Remove the saucepan from heat. Stir in the shredded sharp cheddar cheese, salt, and black pepper until the cheese is fully melted and the sauce is smooth. Gently fold in the cooked elbow macaroni. Allow this mixture to cool for 10 minutes.
05 - In a large mixing bowl, combine the ground beef, breadcrumbs, large egg, grated Parmesan cheese, chopped fresh parsley, garlic powder, onion powder, salt, and black pepper. Mix until all ingredients are just incorporated; avoid overmixing.
06 - Take approximately 2 tablespoons of the meat mixture and flatten it into a disc in the palm of your hand. Place one heaping teaspoon of the cooled mac and cheese mixture in the center of the meat disc. Carefully seal the meat around the filling, shaping it into a ball. Repeat this process with the remaining meat and mac and cheese mixture.
07 - Place the prepared stuffed meatballs onto the lined baking sheet, ensuring they are not overcrowded.
08 - Bake for 20-22 minutes, or until the meatballs are nicely browned and cooked through.
09 - If desired, spoon marinara sauce over the baked meatballs and sprinkle with shredded mozzarella cheese. Return to the oven for an additional 5 minutes, or until the cheese is melted and bubbly.
10 - Serve the Mac and Cheese Stuffed Meatballs hot. Garnish with additional fresh parsley if desired.