To ensure perfect Alfredo make sure you use freshly grated cheeses. The canned stuff may seize and ruin the dish. Also, when adding cheese to any sauce (or soup) you need to make sure the temperature of the sauce is not higher then 180 degrees. When adding cheeses at temperatures over 180 degrees the cheese will actually go through a separation process rather than a melting process (cheeses like to melt slowly at lower temps) and results in a less than smooth end product. Serve over your favorite pasta.