In a large mixing bowl, combine the ground beef, egg, breadcrumbs, grated Parmesan, chopped parsley, minced garlic, salt, and black pepper. Mix gently until just combined, then scoop and roll into 1-inch meatballs.

Heat olive oil in a large skillet over medium heat. Add meatballs in batches and cook for 6-8 minutes until browned. Transfer to a plate and keep warm.

In the same skillet, reduce heat and add butter and minced garlic. Sauté for 1-2 minutes until fragrant. Optional: add red pepper flakes. Stir in lemon juice and parsley.

Return meatballs to the skillet, coat with garlic butter, and simmer for 5-7 minutes to heat through.

Cook linguine in salted boiling water according to package instructions. Reserve ½ cup pasta water, then drain.

In a saucepan, melt butter, add heavy cream, and simmer while stirring. Mix in grated Parmesan until melted and thickened. Adjust thickness with reserved pasta water.

Toss cooked linguine with the creamy sauce, top with meatballs, and drizzle remaining garlic butter sauce over. Garnish with parsley and Parmesan.