Combine ground beef, egg, breadcrumbs, Parmesan, parsley, minced garlic, salt, and pepper in a large bowl. Mix until just combined and form into 1-inch balls.

Heat olive oil in a skillet over medium heat. Add meatballs in batches and sear for 6 to 8 minutes until golden brown. Remove and set aside.

In the same skillet, lower heat and add butter, minced garlic, and red pepper flakes. Cook until fragrant, then stir in lemon juice and parsley. Return meatballs to skillet and simmer for 5 to 7 minutes.

Cook linguine according to package directions. Reserve pasta water before draining. In a saucepan, melt butter, add heavy cream, and stir in Parmesan until smooth. Adjust consistency with reserved pasta water.

Toss cooked linguine in the creamy sauce, plate with meatballs on top, drizzle with extra sauce, and garnish with parsley and Parmesan.