I came upon a recipe similar to this and modified it a little. It turned out to be the easiest and most delicious Alfredo sauce I have ever made. Enjoy!
I also often steam some broccoli and mushrooms and serve this with grilled chicken breast.
While pasta is cooking in a heavy bottom pan, on medium heat, melt butter and the 1 1/2 cups of heavy cream, stirring occasionally. Once combined add 1 1/2 cups of the Parmesan cheese and stir occasionally until melted. Add garlic powder.
Add the corn starch to the remaining 2 T of heavy cream with a fork or small whisk until it makes a smooth paste. This will be what thickens your sauce. Add 1-2 T of the corn starch depending on how thick you would like your sauce. I usually use 1 1/2 T. Once ingredients in pot have combined add the paste to your sauce with a whisk until completely dissolved. It does not take long for your sauce to thicken.
Pour sauce over cooked and drained pasta and mix well. Sprinkle with the remaining Parmesan cheese and serve.