01 - Pulse the sugar and lilac blossoms in a food processor until flowers are finely chopped and sugar becomes fragrant with pale purple hue. Set aside for later use.
02 - Whisk together the all-purpose flour, baking powder, and salt in a medium bowl until thoroughly blended. Set aside.
03 - Beat the softened butter and prepared lilac sugar together in a large bowl until mixture becomes light, fluffy, and pale in color, approximately 3-4 minutes.
04 - Add the large egg and vanilla extract to the butter mixture. Beat until fully incorporated and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Do not overmix.
06 - Divide dough in half and shape each portion into a flat disc. Wrap tightly in plastic wrap and refrigerate for at least 1 hour until firm.
07 - Preheat oven to 350°F. Line baking sheets with parchment paper and set aside.
08 - Roll out chilled dough on lightly floured surface to 1/4 inch thickness. Cut into desired shapes using cookie cutters.
09 - Place cut cookies on prepared baking sheets. Bake for 8-10 minutes until edges are just beginning to turn golden.
10 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely before serving.