Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.

In a large bowl, cream together softened butter and powdered sugar until light and fluffy (about 2–3 minutes).

Add vanilla extract and almond extract (if using). Mix until combined.

In a separate bowl, whisk together flour and cream of tartar. Gradually add dry ingredients to the wet mixture until a soft dough forms.

Divide dough in half and add green food coloring to one portion. Mix until evenly colored.

Wrap dough in plastic wrap and chill for 30 minutes.

Roll dough to ¼-inch thickness on a lightly floured surface.

Cut into shamrock shapes using a cookie cutter.

Place cookies 1 inch apart on prepared baking sheets.

Sprinkle with green sanding sugar if desired.

Bake for 10–12 minutes, or until edges are lightly golden.

Allow cookies to cool completely before decorating with icing if desired.