Steak Diane is a classic recipe that tops your favorite steak with a sauce made with cream, cognac, shallots, beef stock, dijon mustard, and Worcestershire sauce. It's perfect for special occasions but also quick & easy enough for weeknight dinners.
Heat 1 Tablespoon butter and 1 Tablespoon olive oil in a large skillet over medium-high heat. Lightly season 2 8-ounce top sirloin steaks with salt and pepper, and add to skillet; cook, about 4-5 minutes per side, until browned and cooked to desired doneness. When the steaks are done, move to a plate and tent with foil.
Return the skillet to medium-high heat and sauté the 1 small shallot for 1-2 minutes, until softened.
Add the 1/4 cup cognac and cook until the cognac is almost evaporated, about 2 minutes, scraping any browned bits from the bottom of the skillet.
Stir in the ½ cup beef stock and bring to a boil over high heat. Cook until thickened, about 2-3 minutes.
Stir in the ⅓ cup heavy cream and cook for 2 minutes.
Stir in 1 teaspoon Dijon mustard and ½ teaspoon Worcestershire sauce, and then return steaks and any accumulated juices to skillet; cook, turning in sauce, until warmed through, about 3 minutes.
Transfer steak to serving plates and stir 1 Tablespoon fresh parsley and 1 Tablespoon chives into sauce. Season with salt and pepper to taste. Pour sauce over steaks and serve.