• Line the baking sheets with parchment paper. Set aside.

Make the lavender sugar

• Blend the dried lavender and sugar in a food processor until the flowers are finely ground. (If you don't have a food processor, you could use a mortar and pestle, instead.) Set aside.

Make the cookies

• Whisk together the flour, cornstarch, baking powder and salt in a mixing bowl. Set aside.
• In another large mixing bowl, beat the butter with the lavender sugar and lemon zest until it's fluffy and well combined.
• Add the egg and the vanilla and mix to combine.
• Gradually add the flour mixture and beat until it's crumbly.
• Use your hands to squeeze the crumbles until the dough comes together. You may need to add a little more flour, a tablespoon at a time if the dough is too wet. The dough should come together in one piece.
• Cut the dough in half and roll it between 2 sheets of parchment paper, about ¼ inch (0.6cm) thick. Then put the rolled out dough in the freezer for 15 minutes.
• Meanwhile, preheat the oven to 350°F / 180°C.
• Take the dough out of the freezer and use cookie cutters to cut out shapes.
• Place the cookies about 2 inches apart on the prepared baking sheet and bake for about 15 minutes, until they're light golden brown on the edges. (I bake them one tray at a time.)
• Re-roll the dough scraps and repeat the procedure with the other piece of dough.
• Transfer the baked cookies to a wire rack and let them cool completely.

Make the lemon glaze (Optional)

• Whisk together the powdered sugar and lemon juice in a small bowl.
• Drizzle over the cooled cookies.
• Enjoy!