Preheat oven to 180C/350F/Gas 4 and line the two cookie sheets with parchment paper or a non-stick baking sheet.
Using an electric handheld or stand mixer, beat together the butter, powder sugar, egg, and rum extract until combined.
In another bowl, whisk or sift together the flour, baking soda, and baking powder until combined.
Gradually beat the dry ingredients into the wet until a dough forms.
Use a medium-sized ice cream scoop, scoop out some dough onto the cookie sheet.
Gently press the dough down into a thick mound.
Bake 10-12 minutes or until light brown around the edge.
Allow the cookies to cool completely for 10 minutes on the baking sheet before transferring to a wire rack to cool completely.
Using an electric mixer again, beat all frosting ingredients together until smooth and stiff.
Scoop some frosting out onto the cookies and gently spread evenly.
Decorate the top of the cookies with the sanding sugar sprinkles.
Allow the frosting to set before serving.
Enjoy and Laissez Les Bon Temps Rouler!