Generously season each side of the steaks with salt and pepper. Let stand at room temperature about 20 minutes before cooking.
In a cast-iron (or other heavy-duty) skillet, heat 1 tablespoon of the butter over medium heat. Add half of the shallots and saute until tender for a couple of minutes. Stir in the mushrooms and cook until the water has evaporated, about 5 minutes. Season with salt and pepper. Transfer the cooked mushrooms to a dish and set aside. Wipe the skillet clean.
Heat another tablespoon of butter over high heat in the skillet. It will bubble and foam, and after it stops, add the steaks. Sear on each side for about 4 minutes. Transfer to a plate and tent with foil.
Reduce the heat to medium high. Add the remaining shallots and saute for 1 to 2 minutes. Turn the flame off and add the wine. Turn the flame back on to high, bring to boil and let reduce by half. Whisk in the remaining tablespoon of butter. Stir in the reserved mushrooms.
Spoon the sauce over the steaks and serve.