Coat both sides of steak with crushed peppercorns. Melt butter in cast iron skillet. Place steak in pan and cook on one side approximately 6 minutes; turn and cook an additional 4 minutes for medium rare. Remove steak from pan and place on warm platter. Pour off butter; deglaze pan with whiskey. Set on fire. When flame goes out, continue to cook 1 minute. Add heavy cream and cook on high to reduce. When sauce thickens, add parsley and ladle onto steak. Serve.