Cook the linguine in salted boiling water until al dente. Reserve ½ cup pasta water, then drain.
Heat olive oil in a large skillet over medium heat. Add the ground beef and cook for 6 to 8 minutes until browned. Drain excess grease if needed.
Add the butter and garlic to the skillet. Cook for 1 minute until fragrant.
Pour in the beef broth and heavy cream. Stir well and simmer for 3 to 4 minutes.
Add the cheddar, Parmesan, Italian seasoning, red pepper flakes if using, salt, and black pepper. Stir until smooth and creamy.
Add the cooked linguine and toss until coated. Add a splash of pasta water if the sauce is too thick.
Cook for 1 to 2 minutes until everything is hot and creamy.
Garnish with parsley and serve warm. Store leftovers covered in the fridge for up to 3 days.
