In a large mixing bowl, combine ground beef, egg, breadcrumbs, Parmesan cheese, parsley, garlic, salt, and pepper. Mix gently until just combined. Form into 1-inch meatballs and place on a plate.

Heat a large skillet over medium heat, add olive oil, and sear meatballs in batches for 6-8 minutes until golden brown. Transfer to a plate.

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

Return meatballs to the skillet, gently coating with sauce. Simmer for 5-7 minutes until cooked through and internal temperature reaches 160°F.

Meanwhile, boil salted water and cook linguine according to package instructions. Reserve pasta water before draining.

In a separate saucepan, melt additional butter, add heavy cream, and simmer. Stir in extra Parmesan and adjust with reserved pasta water as necessary.

Plate the creamy linguine, top with meatballs, and drizzle with garlic butter sauce. Garnish with parsley and Parmesan.