📖 Instructions

1. Cream the Butter and Sugar: In your large mixing bowl, using an electric mixer (either a stand mixer with the paddle attachment or a hand-held mixer), cream together the softened unsalted butter and granulated sugar on medium speed. Beat them until the mixture is light, fluffy, and noticeably pale in color, which usually takes about 2 to 3 minutes. Don't rush this step; it's what makes the cookies tender!
2. Add the Egg and Vanilla: Scrape down the sides of the bowl with a rubber spatula to ensure everything is well combined. Add the large egg and the vanilla extract. Beat again on medium speed until just combined, about 30 seconds. Be careful not to overmix here.
3. Whisk Dry Ingredients: In a separate, medium-sized bowl, whisk together the all-purpose flour, baking powder, and salt. Whisking ensures these ingredients are evenly distributed, which is crucial for a consistent cookie texture.
4. Combine Wet and Dry: Gradually add the dry ingredient mixture to the wet ingredients in the large mixing bowl. Start on low speed and mix until the flour is *just* incorporated and a soft dough forms. Avoid overmixing, as this can develop too much gluten and result in tough cookies. The dough might look a little crumbly at first, but it will come together.
5. Form and Chill the Dough: Gather the dough into a ball and divide it in half. Flatten each half into a disc, wrap tightly with plastic wrap, and refrigerate for at least 1 hour. Chilling is super important; it prevents spreading and makes the dough much easier to roll and cut. If you're short on time, 30 minutes in the freezer works too!
6. Preheat Oven and Prep Baking Sheets: While your dough chills, preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper. Parchment paper is a lifesaver for preventing sticking and making cleanup a breeze.
7. Roll Out the Dough: On a lightly floured surface (or between two sheets of parchment paper if you prefer less mess), unwrap one disc of chilled dough. Use a rolling pin to roll the dough out to an even thickness of about 1/4 inch. If the dough starts to get too sticky or warm, pop it back in the fridge for 10-15 minutes.
8. Cut Out Cookies: Use your favorite cookie cutters to cut out shapes from the rolled dough. Try to get as many cookies as you can from each roll to minimize re-rolling scraps. Carefully transfer the cut-out cookies to your prepared baking sheets, leaving about 1 inch between each cookie.
9. Bake the Cookies: Bake one sheet at a time in the preheated oven for 8-10 minutes, or until the edges are lightly golden and the centers look set but are still soft. Don't overbake, or they'll lose their tender chewiness! For perfectly even baking, you might want to rotate the baking sheet halfway through.
10. Cool Completely: Let the cookies cool on the baking sheets for about 5 minutes before carefully transferring them to a wire cooling rack to cool completely. They must be entirely cool before icing, or your icing will melt!
11. Make the Smooth Vanilla Icing: While the cookies cool, prepare the icing. In a small mixing bowl, sift the powdered sugar. Sifting is important here to avoid any lumps in your smooth icing. Add the softened unsalted butter, milk, and vanilla extract.
12. Mix the Icing: Using a whisk or a hand mixer on low speed, beat the ingredients until they are fully combined and the icing is smooth and creamy. If the icing is too thick, add a tiny bit more milk (1/2 teaspoon at a time). If it’s too thin, add a bit more sifted powdered sugar. You want a consistency that's easy to spread but not runny.
13. Decorate with Icing and Sprinkles: Once the cookies are completely cool, spread a thin, even layer of the vanilla icing over each cookie using an offset spatula or a small knife. Immediately sprinkle with your favorite festive sprinkles before the icing sets. Allow the icing to set for at least 1-2 hours at room temperature, or until firm to the touch, before stacking or storing.