Here is the recipe from an old Quick Cooking (TOH) magazine. I have made this several times.
Cheddar Spirals
1 pkg (16oz) spiral pasta
2 cups half and half
1 can (10-3/4oz) condensed cheddar cheese soup, undiluted.
1/2 cup butter, melted
4 cups (16oz) shredded cheddar cheese
Cook pasta according to package directions; drain. In a 5-qt crock pot, combine the cream, soup and butter until smooth. Stir in cheese and pasta. Cover and cook on low for 2-21/2 hrs or until cheese is melted. Yield 12-15 servings.
My only suggestion is to heat the cream in the microwave with the butter, until the butter is melted and then add soup and continue as directed. If you melt the butter and add to the cold cream the butter will form clumps.