01 - Pulse the sugar and lilac blossoms in a food processor until flowers are finely chopped and sugar becomes fragrant with a pale purple tint. Set aside for later use.
02 - Whisk together the all-purpose flour, baking powder, and salt in a medium bowl until thoroughly blended.
03 - Beat the unsalted butter and prepared lilac sugar in a large bowl until the mixture becomes light and fluffy, approximately 2-3 minutes.
04 - Incorporate the large egg and vanilla extract into the butter mixture, beating until fully combined and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing until just incorporated. Avoid overmixing to prevent tough cookies.
06 - Divide the dough into two equal portions, shape each into a flat disc, wrap tightly in plastic wrap, and refrigerate for a minimum of 1 hour.
07 - Preheat the oven to 350°F. Line baking sheets with parchment paper and set aside.
08 - Roll out the chilled dough on a lightly floured surface to 1/4 inch thickness. Cut into desired shapes using cookie cutters.
09 - Arrange cutouts on the prepared baking sheets. Bake for 8-10 minutes, or until edges are just beginning to turn golden.
10 - Let cookies rest on the baking pan for 5 minutes before transferring to a wire rack to cool completely.