Step 1

Heat oil in a large saucepan over medium heat. Add bacon and cook, turning occasionally, until crisp, 4 to 5 minutes. Transfer to a paper towel to drain, leaving the oil and bacon drippings in the pan. Add onion to the pan and cook, stirring, until starting to soften, 2 to 3 minutes. Add potatoes and broth. Bring to a boil. Reduce heat to maintain a simmer and cook until the potatoes are tender, 12 to 15 minutes.

Step 2

Using a slotted spoon, transfer about half the potatoes to a bowl and mash until almost smooth, but still a little chunky. Return the mashed potatoes to the pan along with sour cream, 1/4 cup cheese and pepper. Cook, stirring, until the cheese is melted and the soup is heated through, 1 to 2 minutes. Serve garnished with crumbled bacon, the remaining 1/4 cup cheese and chives (or scallion greens).