Preparation

• Position a rack about 6 inches from the broiler element, and heat the broiler on high.Line a large rimmed sheet pan with aluminum foil and mist it with cooking spray.
• Place the Brussels sprouts on the prepared pan, drizzle with 3 Tbs. of the oil, sprinkle with 1/4 tsp. each salt and pepper, toss to coat, and arrange in an even layer.
• Spray a wire rack with cooking spray, and place it over the sprouts, nudging them so the rack lies flat. Brush the steaks with 1 Tbs. of the oil and season both sides with salt and pepper. Place on the rack.
• Broil, flipping the steaks once, until the sprouts are tender and charred on the edges and the steaks are cooked to your liking, 3 to 5 minutes per side for medium rare (125°F to 130°F).
• Meanwhile, purée the sour cream, blue cheese, vinegar, and the remaining 2 Tbs. oil in a food processor or blender until smooth.Season to taste with salt and pepper. Transfer to a bowl and stir in the chives.
• Allow the steak and sprouts to rest for 10 minutes. Transfer the steak to a cutting board and thinly slice. Toss the sprouts to combine the more charred ones with the less charred ones. Stir the sauce and thin with water, if needed.
• Serve the steak and sprouts with the blue cheese sauce.