Pat the strips dry, then sprinkle with salt and pepper. In a large skillet over medium-high heat, warm 1 tablespoon olive oil until shimmering. Add half the beef in a single layer—don’t crowd the pan—and sear 1–2 minutes per side until browned. Transfer to a plate and repeat with remaining beef.

Reduce heat to medium, add the other tablespoon of oil, then stir in onions. Cook 3–4 minutes until translucent. Toss in mushrooms and cook another 5 minutes until they release moisture and turn golden.

Stir in garlic and flour, cooking 1 minute until fragrant (this helps thicken). Gradually pour in beef broth, scraping up brown bits on the bottom—those are flavor gold. Whisk in Dijon mustard and smoked paprika.

Return beef along with any resting juices to the pan. Lower heat and let everything simmer gently for 5–7 minutes, until the sauce thickens and beef is cooked through.

Remove pan from heat, stir in sour cream until velvety smooth. Avoid boiling after adding dairy to prevent curdling. Taste and adjust seasoning.

Plate over cooked egg noodles (or mashed potatoes). Sprinkle with chopped parsley, a twist of black pepper, and maybe a few extra mushroom slices for good measure.