In a medium bowl, combine 100g of sugar with minced fresh basil leaves. Rub until fragrant and light green.

Sift together 200g of all-purpose flour, 1 tablespoon of cornstarch, 1 teaspoon of baking powder, and a pinch of salt in a separate bowl.

In a large bowl, beat 100g of softened butter and the basil sugar until pale and fluffy, about 2-3 minutes.

Blend in 150g of sugar, lemon zest, an egg, and 1 teaspoon of vanilla extract into the creamed butter.

Gradually add the sifted dry ingredients to the wet mixture and gently fold until dough comes together.

Wrap the dough in plastic wrap and refrigerate for at least one hour.

Preheat your oven to 350°F (175°C). Shape dough into balls, roll each in finishing sugar and basil, and place on a baking sheet.

Bake for about 10 minutes or until edges are lightly golden; centers should still be soft.