They key to cooking these skewers evenly on the grill is to make sure your steak, potato and mushroom pieces are roughly the same size so they all touch the grill if skewered together. If they are not the same size, thread them each onto separate skewers.
Cut steak into 1½-inch cubes, toss with 1 Tbsp. Santa Maria and set in refrigerator to marinate for 30 min. Cut potatoes into 1½-inch cubes, add to a large pot, cover with cold water, add a couple dashes of salt and bring to a boil. Boil potatoes until fork tender. (The potatoes won’t spend a lot of time on the grill, so they need to be tender enough to eat, but not so soft that they fall apart when skewered.) Drain potatoes and rinse in cold water. Preheat grill to medium-high. Thread skewers, alternating steak, potato and mushroom (whole or halved) pieces. Combine remaining Santa Maria with melted butter and brush half of the mixture onto skewers. Place skewers on grill and cook until steak reaches desired doneness, about 5 min. for medium-rare to 10 min. for well done. Turn skewers a couple of times for even cooking and brush with remaining Santa Maria butter glaze half way through cooking.
Serve skewers hot or at room temperature. Delicious paired with our Black & Bleu Cheese Dressing as a dip on the side, or remove pieces from skewer and toss with the dressing for a new twist on a potato salad.