In a small bowl, place the dried mushrooms in the boiling water and let sit for 15 minutes. Prepare remaining ingredients. In a small saute pan, place shallot, port, mushrooms and mushroom liquid – simmer until reduced. Liquid should be nearly gone. Let cool. In a food processor, place the softened butter, sage, port/mushroom reduction, salt and freshly ground pepper and pulse several times until mushrooms are minced and all ingredients are incorporated. Place mixture on a piece of parchment paper and roll into a log twist ends to enclose (you can also do this in plastic wrap if you prefer). Place in refrigerator for 15-20 minutes or until ready to use. You can freeze the left over butter for another use.
Heat grill on medium high until hot, oil grates. Sear steak on both sides then finish on indirect heat of grill until cooked to your taste. 125-130 medium rare. Let rest 7-10 minutes. Slice the meat against the grain. Serve steak with a slice of porcini port butter. Serves 4.