Cook 3 slices of 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 ¼ cup sour cream, ¼ cup mayonnaise, 4 teaspoons vinegar, ¼ teaspoon pepper and the reserved bacon fat together in a large bowl. Add 4 cups broccoli, ½ cup scallions, ½ cup cheese and the chopped bacon. Stir to coat with the dressing.
