Gather all the ingredients needed for the cookies.
Using a Stand or Handheld Mixer, combine the Butter, Salt, Maple Sugar and Maple Extract; beat until creamy and smooth.
Add the Powdered Sugar to the Butter mixture and mix on the lowest setting, scraping the sides of the bowl as needed, until well-blended and smooth.
In a small bowl, measure out the 1 1/2 Cups Flour using the "spoon and scrape" method (using a spoon, scoop out the GF Flour into a Dry Measuring Cup, overfilling the cup; then scrape off the excess flour back into the flour bag/container using the back edge of a knife); gently pour the measured GF Flour into the small bowl.
Add the Xanthan Gum (if your GF Flour mix doesn't contain it) to the GF Flour in the small bowl and mix well.
With the mixer set on the lowest setting, gradually add the GF Flour mixture, 1/2 cup at a time, to the Butter mixture; mix well and scrape sides of bowl as need between each addition of the Flour.
Note: the cookie dough will be crumbly, but should hold together when squeezed into a ball; if the dough does not hold together, add 1/2-1 more Tablespoon of softened unsalted butter.
Form the cookie dough into a ball and wrap in plastic wrap; Refrigerate for 30 minutes.
While the dough is in the refrigerator, line 1-2 cookie sheets with parchment paper or baking mats; set aside.
Preheat oven to 325 degrees.
After 30 minutes, remove cookie dough from refrigerator and cut in half for a more manageable portion of dough to roll out.
Note: if the dough is refrigerated for more than 30 minutes, set it out on your kitchen counter for about 15-20 minutes to soften up a little before trying to roll it out.
Once the dough is ready, roll it out onto a lightly floured surface to about 1/4" thickness.
Using the desired cookie cutter/cutters, cut dough into shapes and place onto the prepared cookie sheet/sheets.
Bake for 18-20 minutes, or until cookies are a light golden brown; cool on baking sheets. Enjoy as single Maple Shortbread Cookies or fill with the Maple Buttercream filling (recipe below).