Creamy Cauliflower and Cheddar Soup - Sandra's (Suzanne)

2 tbsp butter
1/2 cup chopped onion
10 oz can chicken broth
1/4 cup flour
2 1/2 cups milk
1 1/2 cups grated cheddar cheese
1 head chopped cauliflower


Saute onion in butter until tender in a large pot.  Add cauliflower and chicken broth; bring to a boil.  Cover, reduce heat and simmer for 15 minutes.  Combine flour and milk until smooth and add to pot.  Cook until thickened.  Remove from heat and stir in cheese, adding salt and pepper to taste.