1-First, adjust oven rack to middle position and preheat oven to 400°F (200°C). Line two sheet pans with parchment paper to prevent sticking and ensure even baking.

2-Second, in a medium bowl, whisk together the flour, baking powder, and baking soda until well combined.

3-Third, in a mixer fitted with the paddle attachment, beat the butter on medium speed until creamy, about 1 minute, to create a smooth base.

4-Fourth, add both sugars and salt; beat on medium speed until the mixture is light and fluffy, about 2-3 minutes, for that perfect texture.

5-Fifth, scrape down the sides of the bowl, then add the egg, egg yolk, and vanilla extract; continue mixing until smooth to incorporate everything evenly.

6-Sixth, add the flour mixture and beat on low speed until just combined. Finish mixing by folding gently with a rubber spatula to avoid overworking the dough.

7-Seventh, shape the dough into balls weighing about 2 tablespoons (50 g) each. Place the balls on a prepared sheet pan and chill in the freezer for about 20 minutes until firm.

8-Eighth, place 8 dough balls per sheet pan and optionally sprinkle each with flaky salt for added flavor.

9-Ninth, bake one pan at a time, rotating halfway through baking, for 8 to 11 minutes until the cookies are golden brown on top and slightly puffed.

10-Tenth, remove from the oven and gently press the center of each cookie with the back of a spoon to enhance the shape.

11-Eleventh, let cookies rest on the sheet pan for 5 minutes, then transfer to a wire rack to cool completely before enjoying.