Step 1
Stir flour and baking powder together in a bowl.
Step 2
Beat butter and white sugar together in the bowl of a stand mixer using the paddle attachment until light and fluffy about 3 minutes. Add egg and vanilla extract; beat 1 minute more. Slowly add flour mixture and blend until dough begins to pull away from the sides of the bowl.
Step 3
Turn dough onto a piece of parchment paper. Knead dough a few times using your hands and form into 2 discs. Wrap each dough disc in plastic wrap and refrigerate for 2 hours.
Step 4
Preheat oven to 350 degrees F (175 degrees C). Line a baking sheet with a silicone mat.
Step 5
Remove 1 disc of dough from the refrigerator. Place dough on a lightly floured work surface; top with a piece of parchment paper. Roll out dough to about 1/3-inch thickness. Cut dough with round cookie cutters and transfer to the prepared baking sheet.
Step 6
Place baking sheet with cookies on it in the freezer or refrigerator for 3 to 5 minutes.
Step 7
Bake in the preheated oven until cookies are just barely beginning to turn golden brown 8 to 10 minutes. Cool cookies on the baking sheet for 1 minute; transfer to a wire rack to cool completely. Repeat with second disc of dough.
Step 8
Wipe down all equipment for making the icing with vinegar including spatulas measuring cups and bowls.
Step 9
Combine confectioners' sugar and meringue powder in the bowl of a stand mixer using the paddle attachment.
Step 9
Mix water corn syrup and clear vanilla extract together in a separate bowl. Pour water mixture into sugar mixture and beat on medium speed until stiff peaks form in the icing 4 to 5 minutes.