Step 1: In a large bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking soda, and salt. Set aside.
Step 2: In the bowl of a stand mixer fitted with the paddle attachment, cream together the softened unsalted butter and granulated sugar on medium-high speed until light and fluffy, about 2-3 minutes.
Step 3: Beat in the large egg and vanilla extract until well combined, scraping down the sides of the bowl as needed.
Step 4: Add the red gel food coloring and mix until the color is evenly distributed throughout the butter mixture. Be generous here to achieve a vibrant red!
Step 5: With the mixer on low speed, gradually add half of the dry ingredients to the wet ingredients, mixing until just combined.
Step 6: Pour in the buttermilk and mix until just incorporated.
Step 7: Add the remaining dry ingredients and mix on low speed until a soft dough forms. Be careful not to overmix!
Step 8: Divide the dough in half, flatten each half into a disc, wrap tightly in plastic wrap, and refrigerate for at least 1 hour (or up to 2 days). This chilling step is crucial for easy handling and preventing the cookies from spreading too much.
Step 9: Preheat your oven to 375°F (190°C). Line baking sheets with parchment paper or silicone baking mats.
Step 10: On a lightly floured surface, roll out one disc of chilled dough to about 1/4-inch thickness. If the dough is too stiff, let it sit at room temperature for 5-10 minutes.
Step 11: Use a Christmas tree-shaped cookie cutter to cut out cookies. Carefully transfer the cutouts to the prepared baking sheets, leaving about 1 inch between them. Gather any scraps, gently re-roll, and cut out more cookies until all dough is used.
Step 12: Bake for 8-10 minutes, or until the edges are set and lightly golden. Do not overbake, as this will make them dry.
Step 13: Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Repeat with the second dough disc.
Step 14: In a medium bowl, beat the softened cream cheese and unsalted butter together on medium speed until smooth and creamy, about 2 minutes.
Step 15: Gradually add the powdered sugar, one cup at a time, mixing on low speed until incorporated, then increasing to medium-high speed until light and fluffy.
Step 16: Beat in the vanilla extract until just combined. If the frosting is too thick, add a tiny splash of milk or cream. If it’s too thin, add a bit more powdered sugar.
Step 17: Once the cookies are completely cool, spread or pipe the cream cheese frosting onto each cookie. For a professional look, you can use a piping bag with a star tip.
Step 18: Decorate with festive sprinkles, edible glitter, or small candies to resemble Christmas ornaments.
Step 19: Allow the frosting to set slightly before serving or storing. Store frosted cookies in an airtight container in the refrigerator.