01 - Preheat oven to 325°F and line two baking sheets with parchment paper.
02 - In a large bowl, beat softened butter and powdered sugar until light and fluffy.
03 - Mix in vanilla extract until fully incorporated.
04 - In a separate bowl, whisk together flour, cornstarch, and salt. Gradually add to butter mixture, mixing until soft dough forms.
05 - Lightly flour work surface and roll dough to 1/4-inch thickness. Cut with round or flower-shaped cookie cutters and transfer to prepared baking sheets.
06 - Gently press an edible flower onto each cookie. Lightly brush tops with egg white to adhere flowers. Sprinkle with granulated sugar if desired.
07 - Bake for 12-15 minutes until edges are just barely golden.
08 - Let cool on baking sheets for 5 minutes, then transfer to wire rack to cool completely.