Step 1: In a large bowl, cream together the softened unsalted butter and granulated sugar with an electric mixer until light and fluffy, about 2-3 minutes.
Step 2: Beat in the large egg and vanilla extract until well combined. Scrape down the sides of the bowl as needed.
Step 3: In a separate medium bowl, whisk together the all-purpose flour, baking powder, and optional salt.
Step 4: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix the dough.
Step 5: Divide the dough in half, flatten each half into a disc, wrap tightly in plastic wrap, and refrigerate for at least 30 minutes, or up to 2 days.
Step 6: Once chilled, preheat your oven to 375°F (190°C). Line baking sheets with parchment paper.
Step 7: On a lightly floured surface, roll out one disc of dough to about 1/4 inch thickness. Use your favorite Christmas cookie cutters to cut out shapes.
Step 8: Carefully transfer the cut-out cookies to the prepared baking sheets, leaving about 1 inch between them. Reroll any dough scraps until all dough is used.
Step 9: Bake for 8-10 minutes, or until the edges are lightly golden. Baking time will vary depending on the size and thickness of your cookies.
Step 10: Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Once cooled, they are ready to decorate!