For the Soft Sugar Cookies:

1. Cream Butter and Sugar: In a large bowl, beat softened unsalted butter and granulated sugar with an electric mixer until light, fluffy, and pale yellow. Scrape down sides of the bowl.
2. Add Egg and Vanilla: Beat in the large egg and vanilla extract until just combined. My tip: do not overmix at this stage!
3. Combine Dry Ingredients: In a separate medium bowl, whisk together all-purpose flour, baking powder, and salt.
4. Gradually Add Dry to Wet: Slowly add the dry ingredients to the wet mixture, mixing on low speed until just incorporated. Remember, do not overmix, or your cookies may become tough.
5. Chill the Dough: Form the dough into a disc, wrap tightly in plastic wrap, and refrigerate for at least 30 minutes, or up to 2 days. This crucial step prevents the cookies from spreading too much during baking.
6. Roll and Cut: On a lightly floured surface (or, my favorite trick, between two sheets of parchment paper), roll out dough to about 1/4-inch thick. Use your favorite cookie cutters to create fun shapes. Reroll any scraps gently.
7. Bake: Preheat oven to 375°F (190°C). Place cut cookies on baking sheets lined with parchment paper. Bake for 8-10 minutes until edges are lightly golden and centers look set but still soft. Do not overbake for that perfectly soft texture of your Soft Sugar Cookie! Let cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.

For the Royal Icing:

1. Whisk Meringue Powder and Water: In a large bowl, whisk meringue powder and warm water until foamy.
2. Gradually Add Powdered Sugar: Slowly add sifted powdered sugar to the meringue mixture, beating on low speed until combined, then increase to medium-high. Beat until thick, glossy, and stiff peaks form (about 5-7 minutes). This creates the base for your beautiful Royal Icing.
3. Divide and Color: Divide icing into separate bowls for different colors. Use gel food coloring for best results, mixing until desired shade is achieved.
4. Adjust Consistency: Add tiny drops of water to achieve desired consistency for outlining (toothpaste-like) or flooding (syrup-like, smooths out in 10-15 seconds).