1/4 cup of the following dry mixture:
1 cup flour
1 cup instant nonfat dry milk
1 1/2 tsp salt
1 cup half-and-half (or whole milk)
2 tbsp butter
1/2 - 1 cup freshly grated parmesan cheese.
 
In a saucepan, over a medium heat, gradually add milk to the dry mixture above. Stir contstantly.
The mixture will thicken in about 2 minutes.
Reduce heat to low and simmer, stirring constantly for about 2 minutes more, stirring in the grated cheese.