You'll need:
- 1 stick butter, at room temperature
- 1/2 c powdered sugar
- 2 tsp lemon extract
- 1 tsp vanilla extract
- 1/4 c corn starch
- 3/4 c flour
First, sift the powdered sugar to remove any clumps. In a stand mixer with the paddle attachment, mix the butter and sugar together until fluffy. Add extracts and mix until incorporated. Sift in the corn starch and flour, and mix until fully blended.
Put the dough in a freezer bag or wrap it in plastic wrap and refrigerate at least half an hour.
Remove dough from the refrigerator and roll out to about 1/4 inch. Cut out the pieces you want - I used a fluted biscuit cutter (from this set of two-sided cutters) - and put them on a plate w/ wax paper. Return the plate with the shortbread cutouts to the fridge for at least 15 minutes.
Put on an ungreased baking sheet - or one lined with parchment paper - and bake 7 to 9 minutes at 350. (Mine were done right at 7 minutes.)
Move to a plate to cool, then dust with powdered sugar.