Combine the whiskey, olive oil, balsamic vinegar, Worcestershire sauce, Dion mustard, dark brown sugar, shallots, garlic, salt and freshly ground black pepper in a bowl. Whisk the ingredients together until the brown sugar has dissolved. Pour the marinade over the steaks and add the rosemary sprigs. (You can do this in a baking pan, a zipper sealable plastic bag or a non-reactive container like a flat ceramic or glass dish.) Pierce the steaks with a paring knife or fork and then massage the marinade into both sides of the steaks and then

Refrigerate for 2 to 4 hours, flipping the steak over halfway during the marinading process. Remove the steak and marinade from the fridge for 30 minutes before you are ready to cook to allow the steak to come to room temperature.

Remove the steaks from the marinade. Transfer the marinade to a small saucepan. Bring the marinade to a boil and then lower the heat and simmer until the sauce thickens, about 7 to minutes. Keep warm.

Pre-heat an outdoor grill, an electric indoor grill or stovetop grill pan to high heat. Place the steak down on the grill and sear both sides for 1 to 2 minutes. Then lower the heat to medium and cook to the desired temperature. Consult the steak chart for desired temperature and remove the steaks from the grill when they are 5 degrees less than the desired doneness.

Let the steaks rest for 5 minutes before serving. Slice and serve the steaks with the cooked whiskey sauce along with a baked potato or other side dishes.