Use a meat mallet to tenderize the meat and then slice into 1/2 inch thick strips.
Heat 1 tablespoon olive oil in a large skillet or pan over medium heat. Add steak strips and cook just until browned. Transfer to a plate and set aside.
In the same pan, add remaining olive oil. Add onion and mushrooms. Cook just until the onions soften and the mushrooms start to brown. Add the garlic, cook 30 seconds.
Whisk in flour and allow to cook for 1 minute. Slowly whisk in the beef broth, Worcestershire, and Dijon. Reduce heat to low and simmer to thicken.
Once the sauce is slightly thickened, reduce heat and add sour cream and thyme. Return steak and any juices that have accumulated to the pan. Stir to combine. Keep on low and allow to simmer while noodles cook.
Meanwhile, once your noodles have cooked, strain them and add them back to the pot but keep them off the heat. Add the butter and stir the noodles until all the butter has melted.
Serve strognaoff over buttered noodles.
Notes
Nutrition information for estimation purposes only.