4 (6-ounce) red potatoes
2 teaspoons olive oil
1/2 cup chopped onion
1 1/4 cups lower-sodium chicken broth
3 tablespoons all-purpose flour
2 cups 1% low-fat milk, divided
1/4 cup reduced-fat sour cream
1/2 teaspoon salt
1/4 teaspoon freshly ground black pepper
3 bacon slices, halved
1/3 cup shredded cheddar cheese
4 teaspoons thinly sliced green onions