1) Beat the butter with the sugars, salt, vanilla, and maple flavor until well blended.
2) Beat in the flour to form a smooth dough. The dough will be crumbly at first, but will come together as it's mixed.
3) Divide the dough in half, pat each half into a disk, wrap well, and chill for about an hour.
4) Preheat the oven to 350°F. Lightly grease (or line with parchment) two baking sheets.
5) Sprinkle the dough and your work surface lightly with flour.
6) Roll the dough till it's a scant 1/4" thick.
7) Cut cookies with a cookie cutter.
8) Place the cookies on the prepared baking sheets, and sprinkle with maple sugar.
9) Bake for 10 to 12 minutes, until they're very lightly browned. Remove from the oven.
10) Let sit on the baking sheet for several minutes before moving to a rack to cool completely.