Wisconsin Cauliflower Soup

2 Tbs. butter/Marg
1 Med Onion chopped (I use 1/2 an onion)
¼ c flour
½ tsp salt
2 cups crème or 1 cup crème 1 cup milk
1 can chicken broth (13-14 oz)
1 head of cauliflower, cut into 1 inch pieces
1 tsp mustard
2-3 cups of sharp cheddar cheese, grated
1/3 cup pepper jack cheese, grated (Not too heavy on the pepper jack...)

In 4 qt. saucepan melt butter over medium heat. Add onion ad cook until golden, about 10 minutes, stirring occasionally. Stir in flour and salt. Cook 2 minutes stirring frequently. Gradually stir in crème, chicken broth, and 1 ½ cups water. Add cauliflower and heat to boiling over high heat. Reduce heat to low. Cover and simmer until cauliflower is tender, about 10 minutes. In a blender, blend cauliflower mixture at low speed at small batches until very smooth. Return cauliflower mixture to saucepan. Heat over medium heat until hot, stirring occasionally. Remove saucepan from heat. Stir in mustard and chesses until melted and smooth. If you reheat this soup later, do not let it boil or the cheese may get stringy.