1. Add milk, cream, salt, dry mustard, pasta and butter into a medium sized pan.2. Bring the mixture to a simmer, stirring frequently, over medium heat. Once at a simmer, turn heat down to low.3. Cook and stir frequently for about 20 minutes, until most of the liquid is absorbed. Add 1/4 more milk if pasta is not fully cooked.4. Remove from heat and stir in cheeses. Cover and let stand for at least five minutes.Add milk, cream, salt, dry mustard, pasta and butter into a medium sized pan.Bring the mixture to a simmer, stirring frequently, over medium heat. Once at a simmer, turn heat down to low.Cook and stir frequently for about 20 minutes, until most of the liquid is absorbed. Add ¼ more milk if pasta is not fully cooked.Remove from heat and stir in cheeses. Cover and let stand for at least five minutes.