Wisconsin Cauliflower Cheese Soup

Yields: 9 cups

2 tablespoons butter (1/4 stick)
1 medium onion, chopped
1 clove garlic, pressed
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 pieces
1 teaspoon Dijon mustard
1 cup shredded sharp Cheddar cheese (about 4 oz)
1 cup pepper jack cheese

In a large pan, melt butter over medium heat. Add onion and cook until golden, about 10 minutes, stirring occasionally. Add garlic for the last minute or so. Stir in flour and salt; cook 2minutes (or until it starts to smell nutty, should not be brown but golden is ok), stirring frequently. Gradually whisk 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 (can use a hand wand). Return cauliflower mixture to saucepan; heat over medium heat until hot, stirring occasionally. Remove saucepan from heat; stir in mustard, pepper jack cheese, and 1/2 cup cheddar cheese until melted and smooth. Garnish soup with remaining cheese.