Melt butter in large saucepan over medium heat. Add olive oil, white onion and the green onion or scallions; cook, stirring occasionally, for 1-2 minutes or until tender. Stir in flour and cook for several minutes. Gradually stir in broth and half and half. Scoop potato pulp from 2 of the potatoes and mash. Add pulp to broth mixture and cook over medium heat, stirring occasionally until mixture comes just to a boil. Dice remaining potatoes and add to soup. Heat through. Season with salt and ground black pepper. Top each serving with bacon, cheese and snipped chives, if desired.