1. Bring a large pot of salted water to a boil. Add the linguine or spaghetti and cook until al dente, according to package instructions. Reserve 1/2 cup of pasta water, then drain the pasta.

2. While the pasta cooks, heat a large skillet over medium-high heat. Add the ground beef, season with salt and black pepper, and cook, breaking it up with a spoon, until browned and cooked through, about 5-6 minutes. Transfer beef to a plate and drain excess fat, leaving about 1 tablespoon in the pan.

3. Reduce the heat to medium. Add the butter to the same skillet. Once melted, add the minced garlic and sauté for 1-2 minutes until fragrant, stirring constantly.

4. Return the beef to the skillet, stirring to combine with the garlic butter. Add the drained pasta, tossing to coat. Pour in about 1/4 cup reserved pasta water, adding more as needed, to help the sauce coat the noodles.

5. Stir in the chopped parsley and grated parmesan cheese until everything is creamy and combined.

6. Serve hot, garnished with extra parsley, more parmesan, and red pepper flakes if desired.