Preheat the oven to 375 degrees F. Combine the first 4 ingredients in shallow-sided plate, and then set aside. Carefully lift the skin up from the thigh end of a chicken leg. Slide of the garlic slices underneath, pushing them to different points around the leg. Repeat with the remaining legs. Brush the top of each leg with mustard. Coat the mustard side with the parmesan mixture, gently patting it on. Place the chicken crust-side up on a baking pan. Bake 45-50 minutes, or until cooked through.