Rich, nutty, iced maple walnut biscotti paired with a steaming mug of coffee is a classic New England favorite. I have made these biscotti with both maple extract and pure maple syrup and find that the extract lends a more robust maple flavor. If you'd rather use maple syrup, then start with 1/4 cup. You'll need to add a bit more flour, though, since the syrup will make it wetter. As for the icing, I prefer syrup. See: http://www.npr.org/2011/01/12/132838584/recipe-maple-walnut-biscotti-with-maple-icing