Horseradish Mustard Sauce ingredients:
Place Worcestershire sauce, olive oil, and chopped rosemary in a small dish and mix well.
Put steaks in a large ziplock freezer bag.
Add Worcestershire mixture. Turn bag a few times to coat meat with the sauce, then press out as much air from the bag as possible. Put in the refridgerator and allow to marinate 6-8 hours, or overnight.
Bring to room temperature and sprinkle with ground pepper.
Prepare a hot fire in a charcoal or gas grill or heat a grill pan over medium-high heat.
Place steaks on grill for about 5 to 6 minutes per side for rare and 7 to 8 minutes for medium rare. Let steaks rest and serve with sauce.
For the horseradish sauce, mix all ingredients in a small bowl and refrigerate for one hour before serving atop the steaks.