01 -
Preheat oven to 190°C. Line two large baking sheets with parchment paper and set aside.
02 -
Melt unsalted butter in a small bowl and cool in the refrigerator for 10 minutes until slightly thickened.
03 -
In a separate bowl, combine flour, cornstarch, baking powder, baking soda, and salt. Whisk until uniformly distributed.
04 -
In a large mixing bowl, vigorously whisk granulated sugar and lemon zest until the mixture resembles wet sand.
05 -
Whisk in cooled melted butter to the sugar-lemon mixture until fully integrated. Add egg, egg yolk, and vanilla extract, whisking until smooth.
06 -
Stir dry ingredients gently into the wet mixture just until incorporated. Avoid over-mixing.
07 -
Fold in blueberries delicately, ensuring even distribution throughout the dough.
08 -
Using a medium cookie scoop (approximately 30 ml), portion dough into balls. Roll balls in granulated sugar if desired.
09 -
Place dough balls on prepared baking sheets, spacing them 8 cm apart to allow for spreading.
10 -
Bake at 190°C for 10 to 12 minutes, or until cookie edges are set and lightly golden. Adjust baking time to 14-16 minutes at 177°C if using frozen blueberries.
11 -
Cool cookies on the baking sheet for 3 to 4 minutes, then transfer to a wire rack to cool completely before serving.