Combine the first 8 ingredients in a bowl. Cover and refrigerate until needed.
Preheat the oven to 450 degrees F. Line a baking sheet with parchment paper. Place the steak, oil, rosemary and mustard in a bowl and toss to combine. Thread a strip of the beef on one end of each skewer and set on the baking sheet. Season with salt and pepper. Bake for 10 minutes, or until cooked to medium-rare. Arrange skewers on a platter with the dip alongside.