01 - Pulse sugar and lilac blossoms in food processor until flowers are finely chopped and sugar is fragrant with pale purple hue. Set aside for infusion.
02 - Whisk flour, baking powder, and salt in medium bowl until uniformly blended.
03 - Beat butter and prepared lilac sugar in large bowl until light and fluffy, approximately 2-3 minutes.
04 - Add egg and vanilla extract to butter mixture, beating until fully combined.
05 - Gradually add dry ingredients to wet mixture, mixing until just incorporated. Avoid overmixing.
06 - Divide dough in half, shape into discs, wrap in plastic, and refrigerate for minimum 1 hour.
07 - Heat oven to 350°F. Line baking sheets with parchment paper.
08 - Roll dough on lightly floured surface to 1/4-inch thickness. Cut shapes with cookie cutters.
09 - Place cookies on prepared sheets. Bake 8-10 minutes until edges are just golden.
10 - Let cookies rest on pan 5 minutes, then transfer to wire rack for complete cooling.