Begin by cooking the rotini pasta. In a large pot, bring water to a boil and add a spoonful of salt. Add the rotini pasta and cook according to package instructions until al dente. Reserve ½ cup of pasta water, then drain the pasta in a colander and set aside.
While the pasta is cooking, heat olive oil in a large skillet over medium heat. Add the ground beef and season with salt and black pepper. Cook, breaking it apart with a spatula, until browned and fully cooked, about 5-7 minutes.
Once the beef is cooked, add the minced garlic to the skillet and cook for an additional 1-2 minutes, stirring frequently until fragrant.
Lower the heat and pour in the heavy cream, stirring to combine with the beef and garlic. Gradually add the grated Parmesan cheese while stirring continuously until the cheese is melted and the sauce is creamy. If the sauce is too thick, add some reserved pasta water to reach your desired consistency.
Add the cooked rotini to the skillet, tossing it well with the sauce. If desired, sprinkle in red pepper flakes for an extra kick. Stir until the pasta is thoroughly coated with the sauce.
Taste and adjust the seasoning if necessary. Serve hot, garnished with chopped fresh parsley.