2 tablespoons butter
1 chopped medium onion
1/4 cup flour
1/2 teaspoon salt
2 cups milk
14.5 ounces chicken broth
1 1/2 cups water
1 head cauliflower (2 1/2 pounds), cut into 1 inch pieces
1 teaspoon Dijon mustard
8 ounces shredded sharp cheddar cheese

In large saucepan, melt butter over medium heat. Add onion, cook and stir 10 minutes till golden. Stir in flour and salt and cook 2 minutes, stirring frequently. Gradually stir in milk, broth and water. Add cauliflower and heat to boiling. Reduce heat, cover and simmer 10 minutes till cauliflower is tender. In food processor, puree mixture in small batches till smooth. Pour mixture back into saucepan. Heat soup, stirring occasionally, till hot. Remove from heat and stir in mustard and cheese till melted and smooth.