Melt butter in pot over medium heat.  Mix in flour, and stir with a whisk. Continuously whisk as you gradually add in milk and chicken broth. As mix thickens add in potatoes and green onion.  Bring to a boil. Continue stirring frequently as mix comes to a boil. Reduce heat and simmer for 10-15 minutes. Mix in salt, pepper, cheese(sour cream if desired) and bacon. Simmer for an additional 10 minutes as cheese melts.