Cauliflower Broccoli Au Gratin Soup

1/2 head cauliflower
2 stalks broccoli
3-4 green onions
3 cups chicken broth
1 small can mushrooms
2 Tbsp butter, melted
4 Tbsp flour
1 Can, 12 oz, evaporated milk
1 1/2 cups cubed cheddar cheese

Cook cauliflower, broccoli and green onion in chicken broth about 12-15 minutes. Stir flour into butter. Add evaporated milk and cook until thickened. Add cheese and allow to melt slightly, add mushrooms. Pour this mixture into vegetables and broth. Heat, but do not boil.