Broccoli Cheese Soup

1/2 cup butter
1 onion, chopped
1 (16 oz) pkg frozen broccoli
4 cans chicken broth
1 lb processed cheese food (Velveeta) OR 4 cups shredded cheddar cheese
2 cups milk
1 tsp garlic powder
2/3 c flour
1 cup water

Cook onion in melted butter until tender. Stir in broccoli and cover with chicken broth and simmer ten minutes. Stir in milk, cheese cubes and garlic powder. Stir until cheese is melted. Mix flour with water and stir into soup to thicken.