In a large saucepan, cook potatoes in boiling salted water for 15 minutes or until tender; drain. In the same saucepan, melt butter over medium heat. Add onion; cook and stir until tender. Stir in flour until blended; gradually add broth and milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Reduce heat; stir in potatoes, salt and pepper. Simmer for 10 minutes or until heated through.
Top each serving with cheese, bacon and additional butter if desired.