01 -
Pound your steak until it's about 0.75cm thick, then slice it into thin strips around 0.5cm wide. Give them a good seasoning with salt and pepper.
02 -
Get your pan nice and hot with some oil. Cook the beef in two batches, spreading it out in one layer. Just 30 seconds each side - you want it browned but still pink inside. Set aside on a plate.
03 -
Turn down the heat a bit, drop in your butter and let it melt. Toss in those onions, cook for a minute, then add mushrooms and cook until they're golden. Scrape up all those tasty browned bits from the pan.
04 -
Dust the veggies with flour and cook for a minute. Pour in your beef broth bit by bit, stirring until smooth. Mix in sour cream and Dijon, then let it bubble and thicken up for 3-5 minutes, stirring occasionally.
05 -
Put your beef back in the pan with all its juices, let it warm through for a minute, then take it off the heat. Spoon it over hot pasta or noodles and sprinkle with chives if you're feeling fancy.