Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper. This prevents sticking and makes cleanup easier.
Cream the butter and sugar together in a large bowl using an electric mixer on medium speed for 2-3 minutes until light and fluffy. Don’t rush this step—proper creaming creates the perfect crumbly texture.
Add the egg and vanilla extract and beat until fully incorporated, about 1 minute. Scrape down the sides of the bowl to ensure even mixing.
In a separate bowl, whisk together the flour, baking powder, and salt to evenly distribute the leavening.
Gradually add the dry ingredients to the wet mixture on low speed, mixing just until combined. The dough should be somewhat crumbly but hold together when pressed.
Scoop tablespoon-sized portions of dough and roll into balls (about 1½-inch diameter). Place on the prepared baking sheets about 2 inches apart.
Gently flatten each ball slightly with the bottom of a glass dipped in sugar to prevent sticking. Don’t press too hard—just enough to create a thick disc.
Sprinkle the tops generously with holiday sprinkles or sparkling sugar, gently pressing them into the surface.
Bake for 10-12 minutes until the edges are just barely turning golden. The centers will look slightly underdone, which is perfect for a crumbly texture.
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. They’ll firm up as they cool while maintaining their delicate, melt-in-your-mouth texture.