Melt butter in large pot, cook onions and green peppers until soft.
Add flour and stir constantly for about 3-5 minutes, flour butter mixture will be thick. Slowly add the milk constantly stirring. Should have a nice thick milk mixture once all the milk is added. Constantly stir until the mixture boils. Add all the broth to the mixture slowly, stirring the entire time. Add cooked sausage and chopped potatoes. Season with salt and pepper. Soup is done once the potatoes have softened.