Question: How can I keep from having a clumpy Alfredo sauce after I add the Parmesan cheese? What am I missing?
First, there is really no such thing as an Alfredo "sauce." There's only a dressing for the pasta.
Here's how the cooks at Restaurant Alfredo in Rome make their famous dish:
Melt the butter in the pan. Salt and pepper, if you like. Then add the freshly-cooked pasta (still very hot) to the butter, mixing it together while keeping the pan on low heat. Mix the cream in to the pasta. The cream and butter will start to be absorbed by the pasta. Then sprinkle on the Parmesan cheese. Keep mixing until the cheese joins with the coating on the noodles. It all takes only about 4 or 5 minutes, or even less. Taste for salt and pepper.
That's the true Alfredo pasta!