Preheat the oven to 325°F. Melt a tablespoon of butter and brush it onto the bottom and sides of a shortbread pan. Alternatively rub soft butter onto the bottom and sides of an 8" round pan., Beat together the remaining 15 tablespoons butter, maple sugar, salt, and flavors until well blended., Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Mix in the flour to form a smooth, cohesive dough. The dough will be crumbly at first, but will come together as it's mixed., Fold in the chopped nuts., Divide the dough in half. Wrap one half in plastic and set aside. Press the second half into the prepared pan., Use a fork to prick the dough all over; this allows any steam to escape, and prevents the shortbread from bubbling as it bakes., Bake the shortbread for 25 to 30 minutes, until the surface is a light golden brown, and the edges are a darker golden brown., Remove the shortbread from the oven, and immediately turn it out onto a clean work surface. Gently brush the shortbread with the maple syrup (you want to be careful not to brush away the pattern if you used a shortbread pan)., Using a pizza wheel or sharp knife, cut the shortbread while still warm into 8 equal wedges and transfer them to a rack to cool completely., Repeat the bake with the remaining half of dough., Store the shortbread, well wrapped, at room temperature for several days; freeze for longer storage.