Wisconsin Cauliflower Soup

I have had my eye on this recipe for the past couple of months, but had never gotten around to making it. A couple of months ago, my parents took Emi and I to Zupas. It is a restaurant that serves soups, salads, and sandwiches and they seem to be sprouting up all over the place now. This wasn't my first experience with Zupas, but it was my husband's and he LOVED it.
My dad's favorite soup is the Wisconsin Califlower Soup, so I was really excited when I found this copy cat recipe. I've never tried it so I didn't know whether the taste was right or not, but my family really liked the soup. We had a couple of setbacks since my mom accidently picked up a mild cheddar cheese and monteray jack with jalapenos instead of pepper jack, but it all turned out in the end. :-D
Good thing I made it because *hopefully* (crosses fingers) last night will be one of the last cold days this season, but it is Utah afterall and we all know how Utah's weather can change.

ZUPAS WISCONSIN CAULIFLOWER SOUP
2 tablespoons margarine or butter (1/4 stick)
1 medium onion, chopped
1/4 cup all-purpose flour
1/2 teaspoon 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 teaspoon Dijon mustard
1 cup Sharp 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 2minutes, 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.