
Boil the egg noodles per the package; drain.
Slice the steak into thin strips, season with salt and pepper, and sear in 1 tbsp butter in a large skillet over high heat, 1-2 minutes per side, until 145°F. Set aside and rest 3 minutes.
Add the remaining butter, sliced onion, and mushrooms; cook 6 minutes until browned. Stir in garlic and flour for 1 minute.
Whisk in the broth and mustard and simmer 3-4 minutes until thickened. Turn heat to low and stir in the sour cream (don't let it boil).
Return the beef and any juices, warm through 1 minute, and serve over the noodles.
Photo: DinnerDrop