Get the ultimate umami flavors in these kabobs of steak, mushroom and onion. J-M Farms Baby Portabella Mushrooms offer serious meatiness and are the perfect size for sliding onto a kabob. We like a cubed sirloin steak for this recipe, but any steak will work great. A marinade of olive oil, balsamic vinegar, mustard and rosemary give a real punch of flavor. Serve these kabobs with rice, grilled potatoes or with a fresh salad.