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

Heat olive oil in a skillet over medium heat. Add meatballs in batches, sear until golden brown on all sides, about 6-8 minutes. Remove and set aside.

In the same skillet, reduce heat to low, add butter, minced garlic, and red pepper flakes. Cook for 1-2 minutes until fragrant. Stir in lemon juice and parsley, then return meatballs and simmer for 5-7 minutes.

Cook linguine according to package directions in salted boiling water until al dente. Reserve ½ cup of the pasta water, then drain.

In a saucepan, melt butter, then stir in heavy cream and bring to a gentle simmer. Stir in Parmesan until melted and adjust consistency with reserved pasta water.

Add cooked linguine to the creamy sauce, toss gently until well coated. Serve with meatballs and drizzle with garlic sauce, garnished with parsley and Parmesan.