In a dutch oven, place potatoes; add just enough water to cover. Heat to boiling. Reduce heat, cover and simmer 10 -15 minutes or until potatoes are very tender. Drain. Reserve 1 cup potatoes; return remaining potatoes to saucepan. In a small bowl, mash potatoes with fork then return to saucepan.

Stir in broth, salt and pepper. Heat to boiling. Add broccoli. Return to boiling; cook uncovered 4 minutes stirring occasionally. Reduce heat to medium.

In small bowl with wire whisk, stir flour into milk until well mixed. Add milk mixture to potato mixture, stirring constantly, Cook over medium heat, stirring frequently, until mixture thickens and boils. Stir in cheese until melted and smooth. Stir in sour cream and green onions; cook until thoroughly heated.