Cook pasta: In a large pot of salted water, cook the pasta according to package directions until al dente. Reserve 1/4 cup of the pasta water, then drain the rest.
Sauté garlic: In a large skillet over medium heat, melt butter. Add the minced garlic and cook until fragrant, about 1 minute.
Make the sauce: Pour in the heavy cream and stir. Let it simmer for 2–3 minutes, then whisk in Parmesan cheese until melted and smooth.
Combine: Add cooked pasta to the skillet, tossing to coat. Use reserved pasta water a little at a time until the sauce reaches your desired consistency.
Season and serve: Season with salt, pepper, and garlic powder if using. Garnish with parsley and extra Parmesan. Serve immediately.