I use 1.5 cups microplaned parmesan, which is probably more than the recipe actually wants, but it works
I have no idea why the original recipe says that parmesan doesn't melt well and she frequently subs gruyere. Don't do this. Parmesan melts fine and why would you want gruyere in your alfredo sauce??
Instructions
Melt butter in medium saucepan over medium-low heat. Add cream, bring to a simmer, and simmer for about 5 - 10 minutes
Add garlic and cheese; whisk quickly until dissolved
Continue simmering until desired thickness is reached