Step 1: In a large mixing bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until the mixture is light, fluffy, and pale yellow. Scrape down the sides of the bowl periodically to ensure even mixing. This usually takes about 2-3 minutes on medium speed.
Step 2: Beat in the large egg and pure vanilla extract until they are well combined with the butter mixture. Continue to scrape the bowl to ensure everything is fully incorporated and smooth.
Step 3: In a separate medium bowl, whisk together the all-purpose flour, baking powder, and a pinch of salt. Gradually add these dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
Step 4: Divide the dough in half, flatten each half into a disk, wrap tightly in plastic wrap, and refrigerate for at least 2 hours, or even overnight. Chilling the dough is essential to prevent spreading.
Step 5: On a lightly floured surface, roll out one disk of chilled dough to about 1/4 inch thickness. Use Valentine’s Day themed cookie cutters to cut out shapes. Carefully transfer the cut-out cookies to parchment-lined baking sheets. Gather dough scraps, re-roll, and cut again.
Step 6: Preheat your oven to 375°F (190°C). Bake the cookies for 8-10 minutes, or until the edges are just lightly golden. Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely. Cookies must be completely cool before decorating.
Step 7: For the Royal Icing: In a large bowl, whisk together the sifted powdered sugar, meringue powder, and 1/2 cup warm water until completely smooth. Start with less water and add more, a teaspoon at a time, until you achieve the desired consistency (thick like toothpaste for outlining, thinner like honey for flooding).
Step 8: Divide the icing into separate bowls for each color. Use gel food coloring for vibrant hues. Keep unused icing covered with plastic wrap pressed directly onto the surface to prevent crusting.
Step 9: Transfer outlining consistency icing to piping bags with small round tips. Outline your cooled cookies and let dry for 10-15 minutes. Thin some colored icing to flooding consistency and fill in the outlined areas using a squeeze bottle or spoon. Use a toothpick to spread and pop air bubbles.
Step 10: Allow your decorated cookies to dry completely, ideally overnight (8-12 hours) at room temperature. This ensures the icing hardens beautifully and prevents smudging. Store in an airtight container.