Melt the butter in a heavy skillet over medium heat and add the olive oil. Brown the steak well on both sides in the hot fat. Remove and set aside.
In the same skillet, sauté the onions until just limp. Add the mushrooms and cook for a couple of minutes. The mushrooms can be left whole, quartered, or halved, depending on their size.
Stir in the catsup, coffee, and whiskey. Return the steak to the skillet, spoon some of the sauce over the meat, cover.
Bake in a preheated 350-degree oven for 15 to 20 minutes.
Cut the steak into thin slices across the grain, on the diagonal. Pour the sauce over the slices and serve.