01 - Pulse the granulated sugar and fresh 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 evenly blended.
03 - Beat the softened butter and prepared lilac sugar in a large bowl using an electric mixer until light and fluffy, approximately 2-3 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 just until the flour disappears. Avoid overmixing to prevent tough cookies.
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 chilled dough on a lightly floured surface to 1/4 inch thickness. Cut into desired shapes using cookie cutters and transfer to prepared baking sheets, spacing 2 inches apart.
09 - Bake for 8-10 minutes until edges are just barely golden. Centers should remain soft for perfectly tender cookies.
10 - Let cookies rest on baking sheets for 5 minutes to set, then carefully transfer to a wire rack to cool completely before serving.