The keys to a good Alfredo sauce are quality ingredients and patience. By quality ingredients, I mean whole butter and an excellent quality Parmesan cheese. Stay away from the pasta aisle in your supermarket when looking for the cheese. Instead, head over to the deli and get the good stuff. This is definitely the time and place to splurge. In addition to tasting better, the real stuff will melt better and leave you with a smooth sauce, whereas the cheap stuff from aisle 6 will leave your sauce gritty.
This sauce needs to cook slowly. I never let the sauce boil. I cook it over very low heat and stir it continuously to prevent scorching the cream. I also add a little cream cheese to help smooth out the flavor and thicken the sauce slightly. If this sauce gets too hot, it can curdle or separate, neither of which is appealing to look at or taste.
2 Tbsp butter
2 cloves garlic (optional for some, a must for me)
12 oz heavy cream
2 oz cream cheese
8 oz freshly grated Parmesan cheese
1/4 tsp nutmeg
1/4 tsp freshly ground black pepper