Beef Stroganoff

• Kosher salt
• 0.75 lb. beef strip or ribeye steak
• Freshly ground black pepper
• 4 tsp. oil
• 2 Tbsp. unsalted butter
• 6 oz. white button mushrooms, sliced somewhat thick
• 0.5 cup finely chopped yellow onion
• 1.5 tsp. all-purpose flour
• 1 tsp. English mustard powder
• 0.5 cup beef broth
• 0.5 cup sour cream (N.B. do not use low-fat—it will curdle), at room temperature
• 6 oz. wide egg noodles
• 1 Tbsp. thinly sliced fresh chives

Bring a large pot of water to a boil over high heat and salt it well.

Season the steak with 0.5 tsp. salt and 0.5 tsp. pepper. Heat 2 tsp. of the oil in a 12" skillet over medium-high heat until very hot. Add the steak and cook for no more than 1 minute on each side, until the meat is just nicely seared; do not overcook it—it will get cooked a little more later. Transfer to a cutting-board and let it rest.

Remove the skillet from the heat. Add 1 Tbsp. of butter and the remaining 2 tsp. oil to the skillet and stir until the butter melts. Put the skillet over medium heat and add the mushrooms.

Cook, stirring occasionally, until the mushrooms release their liquid, about 5 minutes. Add the onions and cook, stirring occasionally, until the liquid has evaporated and the onions are beginning to soften, about 3 minutes more.

Sprinkle the mushroom mixture with the flour and mustard powder and stir for 15 seconds. Stir in the broth and bring to a simmer, scraping up any browned bits in the skillet with a wooden spoon. Add the sour cream and whisk until the sauce is smooth.

Slice the steak into strips 0.25" thick and cut these crosswise into 1" pieces. Add the beef and any juices to the skillet. Cook, stirring often, until the sauce is barely simmering. Season to taste with salt and pepper.

Meanwhile, cook the noodles according to the package directions in the boiling water until barely tender. Drain and return to the pot. Off the heat, add the remaining 2 Tbsp. butter and stir to melt. Season to taste with salt and pepper.

At this point, you may also add the juice of half a lemon and 2 Tbsp. chopped cornichons for a little zing in the tail, should you wish.

Serve the beef Stroganoff over the noodles, sprinkled with the chives.