1.5 pounds beef sirloin steak – thinly sliced across the grain
1.25 tsp kosher salt
0.5 tsp black pepper – freshly ground
1 tbsp neutral oil
3 tbsp unsalted butter
12 ounces cremini mushrooms – sliced
10 ounces onion – thinly sliced
2 cloves garlic – minced
2 tbsp all-purpose flour
1 cup beef stock
1 tbsp dijon mustard
1 cup sour cream – at room temperature
12 ounces egg noodles – for serving
fresh parsley – chopped (for garnish)
Instructions
Pat the beef dry and season evenly with the kosher salt and black pepper.
Heat the neutral oil in a large heavy skillet over high heat until just smoking. Add the seasoned meat in batches and sear 1–2 minutes per side until just browned; transfer to a plate.
Reduce heat to medium. Melt the unsalted butter in the same skillet, then add the cremini mushrooms. Cook, stirring occasionally, until they release liquid and become deeply browned, 6–8 minutes. Add the onion and cook until softened and translucent, 5–7 minutes. Stir in the garlic and cook until fragrant, about 30 seconds.
Sprinkle in the all-purpose flour and cook, stirring, for 1 minute. Whisk in the beef stock and dijon mustard, scraping up any browned bits. Bring to a simmer and cook until slightly thickened and glossy, 3–5 minutes, to a consistency that lightly coats a spoon.
Return the meat and any accumulated juices to the skillet and simmer gently until just cooked through and tender, 2–3 minutes.
Reduce heat to low. In a small bowl, stir the sour cream with a ladle of the hot sauce to temper, then stir it into the skillet. Warm through without boiling, 1–2 minutes. Adjust seasoning to taste and remove from heat.
While the sauce simmers, cook the egg noodles in boiling water according to package directions until just tender; drain well.
Serve the stroganoff over the egg noodles and finish with the fresh parsley.