*Cubes should be big enough for two bites.
In a medkum-size bowl, combine the mustard, Worcestershire sauce, brown sugar and salt and peper to taste. Slowly whisk in the oil. Pour the mixture into a large ziploc bag. Add the sirloin cubes and shake to combine. Refrigerate for at least eight hours or up to overnight.
Prepare the grill. Thread six or seven sirloin cubes onto each skewer. Cook on a well-oiled grill over medium heat about six minutes per side, or until cooked to desired doneness.
Makes 6 servings.
Per serving: 395 calories, 38g prot., 3g carb., 25g. fat., 113 mg chol., 7g sat. fat, 354mg sodium.