Cook bacon in a large skillet over medium heat until crisp, 5 to 7 minutes. Transfer to a paper-towel-lined plate. Reserve 1 tablespoon bacon fat. Chop the bacon when cool enough to handle.
Whisk sour cream, mayonnaise, vinegar, pepper and the reserved bacon fat together in a large bowl. Add broccoli, scallions, cheese and the chopped bacon. Stir to coat with the dressing.
