Step 1: In a large bowl, cream together the softened unsalted butter and granulated sugar with an electric mixer until light and fluffy, about 2-3 minutes.
Step 2: Beat in the egg, ube extract, and optional ube halaya until well combined and the mixture is a uniform vibrant purple color.
Step 3: In a separate medium bowl, whisk together the all-purpose flour, baking powder, and salt.
Step 4: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix the dough.
Step 5: Cover the dough bowl with plastic wrap and chill in the refrigerator for at least 1 hour, or up to 3 hours. Chilling is crucial for the dough to firm up and for the cookies to hold their shape and crinkle beautifully.
Step 6: Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
Step 7: Place the powdered sugar into a shallow bowl. Scoop out dough using a small cookie scoop (about 1 tablespoon per cookie) and roll each portion into a smooth ball. Generously roll each dough ball in the powdered sugar, ensuring it's completely coated.
Step 8: Place the sugar-coated dough balls on the prepared baking sheets, leaving about 2 inches between them.
Step 9: Bake for 10-12 minutes, or until the edges are just set and the centers still look slightly soft. Do not overbake. The powdered sugar will crack, revealing the vibrant purple underneath.
Step 10: Remove from the oven and let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely. Store Ube Crinkles in an airtight container at room temperature for up to 3-4 days.