How to Make It
Cook the bacon in a large skillet over medium heat, stirring occasionally, until crisp, 5 to 7 minutes. Using a slotted spoon, transfer to a paper towel-lined plate. Reserve the skillet.
Add the potatoes to the drippings in the skillet, season with ¼ teaspoon each salt and pepper, and increase heat to medium-high. Cook, tossing occasionally, until browned and tender, 12 to 15 minutes.
Meanwhile, heat the oil in a second large skillet over medium-high heat. Season the steak with ¼ teaspoon each salt and pepper and cook until and instant-read thermometer inserted in each piece register 130ºF, 5 to 7 minutes per side for medium-rare. Let rest at least 5 minutes before slicing.
Mix together the blue cheese, sour cream, buttermilk, vinegar, scallion, and ¼ teaspoon each salt and pepper in a small bowl.
Divide the lettuce among plates, top with the steak, bacon, and potatoes, and drizzle with the dressing.