Directions
Bring a large pot of salted water to a boil for the noodles. Pat the beef dry and season with the salt and pepper.
Heat the oil in a large skillet over medium-high heat. Sear the beef in a single layer, in two batches, for 1 to 2 minutes per side, until browned. Move it to a plate.
Lower the heat to medium. Melt the butter and cook the mushrooms and onion for 7 to 8 minutes, until browned and the liquid has cooked off. Add the garlic for 30 seconds.
Sprinkle in the flour and stir for 1 minute. Pour in the broth and Worcestershire, scraping up the browned bits, and simmer 4 to 5 minutes, until slightly thickened.
Cook the noodles according to the package while the sauce simmers. Drain.
Take the skillet off the heat. Stir in the sour cream until smooth, then return the beef and its juices to the pan. Serve over the noodles.
Tip
Add the sour cream off the heat. Boiling it can make the sauce split.
Storing
Refrigerate up to 3 days. Reheat gently over low heat and add a splash of broth if the sauce is thick.
Swaps
Use ground beef if you prefer; brown it in step 2 and drain extra fat. Check ingredient labels if you cook for someone with an allergy. See the Disclaimer.