Wisconsin Cauliflower Soup

I tasted this soup at a family campout a month or so ago and haven't been able to get it off my mind. I think they put something addictive in it. And since there isn't a Zupas relatively close to my house I had to find a recipe for it online. This one was pretty close but I'm going to make some changes next time I make it.

WISCONSIN CAULIFLOWER SOUP
Yields: 9 cups or 8 first-course servings (or 4-5 hungry adults)

2 T. margarine or butter
1 medium onion, chopped
1/4 c. all-purpose flour
1/2 tsp. salt
2 cups milk
1 can (13 3/4 to 14 1/2 ounces) chicken broth
1 head (2 1/2 pounds) cauliflower, cut into 1-inch pieces
1 tsp. Dijon mustard
1 cup shredded cheddar cheese
1 cup pepper jack cheese

In 4-quart saucepan, melt margarine or butter over medium heat. Add onion and cook until golden, about 10 minutes, stirring occasionally. Stir in flour and salt; cook 2 minutes, stirring frequently. Gradually stir in milk, chicken broth, and 1 1/2 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 blender (with center part of blender cover removed to allow steam to escape), blend cauliflower mixture at low speed in 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 1 1/2 cups cheese until melted and smooth. Garnish soup with remaining cheese to serve.

**When I make this again I'm going to use sharp cheddar (I only had medium) and do 1 1/2 cups cheddar and 1/2 cup pepper jack. The jack was a little too strong for me. And I almost always put in more cheese than recipes say so when I made this the other day I probably used 1 1/2 cups of each.