Pure maple syrup, made from the boiled sap of the sugar maple tree, comes in three grades. Grade A Light or Fancy syrup, sometimes called Grade AA, is clear gold and has a wonderfully subtle flavor, but its delicate character does not hold up in cooking. Grade B syrup is produced only in Vermont and has more maple flavor than Grade A. Sometimes called "baking" or "cooking" maple syrup, it is ideal for use in this recipe. Grade C has a robust, molasses-like flavor and is used primarily in making commercial table syrups.