Preheat your oven to 350 degrees and line 2 cookie sheets with parchment paper.
In a medium bowl, whisk the flour, starch, baking soda and salt.
In a separate large bowl use an electric hand mixer to beat the butter, 1/4 cup of the sugar and the stevia together until well mixed. Add in the egg, egg yolk and extracts and beat until well combined.
Stir the flour mixture in. Cover and refrigerate 15 minutes.
Once chilled, use a cookie scoop to form into 1 Tbsp sized balls and roll each ball into sugar. Place onto the prepared pans and press out just under 1/2 inch thick.
Bake until the top feels set, about 10-11 minutes. Then cool on the pan COMPLETELY (they set up a lot)