Cauliflower Cheese Soup

Heat a large pot over medium-low heat. Add butter and melt. Add chopped onions and cook until translucent, about 5 minutes. Add flour and cook for 3 minutes, stirring occasionally. Slowly stir in the milk, water, and chicken broth. Add cauliflower and salt and heat until boiling. Reduce the heat to low and simmer, covered, until the cauliflower is tender, about 15 minutes.

Using an immersion blender, blend the soup until all the cauliflower chunks are gone. Add mustard and cheeses and stir until melted.

Serve hot with a garnish of cheese on top.