01 - Preheat the oven to 325°F and line two baking sheets with parchment paper.
02 - In a large bowl, cream together the softened butter and powdered sugar until light and fluffy.
03 - Add the vanilla extract and mix to combine thoroughly.
04 - In a separate bowl, whisk together the flour, cornstarch, and salt. Gradually add the dry ingredients to the butter mixture, mixing until a soft dough forms.
05 - Lightly flour a work surface and roll the dough to about 1/4-inch thickness.
06 - Cut out cookies using a round or flower-shaped cookie cutter and transfer to the prepared baking sheets.
07 - Gently press an edible flower onto each cookie. Brush the tops lightly with egg white to adhere the flowers. Sprinkle with granulated sugar if desired.
08 - Bake for 12-15 minutes, or until the edges are just barely golden.
09 - Allow to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.