In a large mixing bowl, combine ground beef, egg, breadcrumbs, grated Parmesan, chopped parsley, minced garlic, salt, and black pepper. Mix gently until just combined, shape into 1-inch meatballs and place them on a baking sheet.

Heat 2 tablespoons of olive oil in a skillet over medium heat. Add the meatballs in a single layer and sear for 6–8 minutes, turning occasionally, until browned on all sides but not fully cooked. Remove from skillet.

In the same skillet, reduce the heat to low and add 4 tablespoons of unsalted butter. Allow to melt, then add minced garlic and red pepper flakes. Sauté for 1–2 minutes until garlic is fragrant. Stir in lemon juice and chopped parsley.

Return the browned meatballs to the skillet, ensuring they're coated in the garlic butter sauce. Cover and let them simmer on low heat for 5–7 minutes, or until fully cooked.

While the meatballs are simmering, cook linguine according to package instructions in boiling salted water for about 8–10 minutes. Reserve ½ cup of pasta water before draining.

In a separate saucepan, melt another tablespoon of butter. Add ½ cup of heavy cream and bring to a gentle simmer. Stir in reserved pasta water and grated Parmesan until creamy. Season sauce with salt and pepper.

To serve, twirl a generous portion of creamy linguine onto each plate, top with several garlic butter meatballs, drizzle with garlic butter sauce, and garnish with chopped parsley and fresh Parmesan.