01 - Pulse the sugar and lilac blossoms in a food processor until the flowers are finely chopped and the sugar becomes fragrant and pale purple. 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 softened butter and prepared lilac sugar together in a large bowl until the mixture becomes light and fluffy, approximately 2-3 minutes.
04 - Add the egg and vanilla extract to the butter mixture, beating until fully incorporated and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing by hand or on low speed just until the flour disappears. Do not overmix.
06 - Divide the dough into two equal portions, shape each into a flat disc, wrap tightly in plastic wrap, and refrigerate for at least 1 hour until firm.
07 - Preheat your oven to 350°F and line baking sheets with parchment paper.
08 - On a lightly floured surface, roll out the chilled dough to 1/4 inch thickness. Cut into desired shapes using cookie cutters and transfer to prepared baking sheets, spacing 1 inch apart.
09 - Bake for 8-10 minutes or until the edges are just beginning to turn golden brown. The centers should still appear slightly soft.
10 - Allow cookies to rest on the baking sheets for 5 minutes, then carefully transfer to a wire cooling rack to cool completely before serving or storing.