Prep: Preheat your oven to 370°F (185°C). Sift the flour and baking powder into a medium bowl and set aside.
Cream: In a large bowl or stand mixer, beat the softened butter and sugar until soft, pale, and fluffy.
Wet Ingredients: Add the whole egg, the extra egg yolk (if using), and the vanilla bean paste. Beat well, scraping down the sides of the bowl to ensure everything is incorporated.
Combine: Gradually add the sifted flour mixture to the wet ingredients. Mix on low speed just until a dough forms and pulls away from the sides. Do not overmix.
Roll: Divide the dough in half. Place each half between two sheets of parchment paper (or plastic wrap). Roll out to approximately 1/4 inch thickness.
Chill: Place the rolled-out dough sheets (still in the paper) onto a cookie sheet and refrigerate for at least 30-60 minutes until firm.
Cut: Peel off the top layer of paper. Use cookie cutters to cut out your desired shapes. Place them on a parchment-lined baking sheet. (Re-roll scraps and chill again if they get soft).
Bake: Bake at 370°F for 12–14 minutes. You are looking for the bottoms to be lightly golden, but the tops should remain pale.
Cool: Allow to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely before decorating.