Cauliflower Cheddar Soup

2 T. butter
1 medium onion, chopped
1/4 c. flour
1/2 tsp. salt
2 c. milk
2 c. chicken broth
1 head cauliflower, cut up
2 c. shredded Cheddar cheese

-In a 4-quart saucepan, add butter over medium heat. Cook onion until golden brown, 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.
-mash cauliflower in blender or food processor until very smooth
-return cauliflower mixture to saucepan; heat over medium heat until hot, stirring occasionally. Remove from heat; stir in mustard and 1 1/2 cups cheese until melted and smooth. Serve!