01 - Pulse the sugar and lilac blossoms in a food processor until flowers are finely chopped and sugar is fragrant with a pale purple hue. Set aside for use.
02 - Whisk together the all-purpose flour, baking powder, and salt in a medium bowl until evenly blended.
03 - Beat the butter and prepared lilac sugar in a large bowl until the mixture is light and fluffy, approximately 2-3 minutes.
04 - Incorporate the egg and vanilla extract into the butter mixture, beating until fully combined and smooth.
05 - Gradually mix in the dry ingredients, stirring just until incorporated. Avoid overmixing to maintain tender texture.
06 - Divide dough in half, form into discs, wrap tightly in plastic wrap, and refrigerate for a minimum of 1 hour to firm.
07 - Preheat oven to 350°F and line baking sheets with parchment paper.
08 - On a lightly floured surface, roll dough to 1/4 inch thickness. Cut shapes using cookie cutters and transfer to prepared baking sheets.
09 - Bake for 8-10 minutes until edges are just beginning to turn golden. Centers should remain slightly soft.
10 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely before serving.