Step 1: In a large mixing bowl, cream together the softened unsalted butter and granulated sugar with an electric mixer on medium-high speed until light, fluffy, and pale yellow, about 3-5 minutes. Scrape down the sides of the bowl as needed.
Step 2: Beat in the large eggs, one at a time, mixing well after each addition until fully incorporated. Stir in the pure vanilla extract.
Step 3: In a separate medium bowl, whisk together the all-purpose flour, baking powder, and salt until well combined.
Step 4: With the mixer on low speed, gradually add the dry ingredients to the wet ingredients, mixing 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 1 hour, or preferably 2-3 hours. Chilling helps prevent spreading and makes the dough easier to handle.
Step 6: Preheat your oven to 375°F (190°C). Line several baking sheets with parchment paper or silicone baking mats.
Step 7: On a lightly floured surface, unwrap one disc of chilled dough. Use a rolling pin to roll the dough to an even ¼-inch thickness. Add a little more flour to your surface if the dough sticks.
Step 8: Use your favorite Christmas-themed cookie cutters to cut out shapes. Carefully place the cutouts about 1 inch apart on the prepared baking sheets. Gather dough scraps, gently re-roll, and cut more cookies.
Step 9: Bake for 8-10 minutes, or until the edges are lightly golden and the centers are just set. Baking time may vary depending on cookie size and oven.
Step 10: Let the cookies cool on the baking sheets for 2-3 minutes before carefully transferring them to a wire rack to cool completely. Ensure they are fully cooled before decorating.
Step 11: Once cookies are completely cool, prepare your desired royal icing, glazes, or buttercream. Arrange an assortment of sprinkles, edible glitter, and other decorations.
Step 12: Decorate your cookies as desired, using various colors, piping techniques, and festive sprinkles. Allow the icing to set completely before storing.