Preheat your oven to 350°F (175°C). This ensures that your cookies bake evenly from the moment you place them in the oven.
In a mixing bowl, combine the softened unsalted butter and granulated sugar. Using a hand mixer or stand mixer, beat the mixture on medium speed until it becomes light and fluffy, about 2-3 minutes.
Add the large egg yolk and vanilla extract to the creamed butter and sugar. Mix until fully combined. The mixture should be smooth and creamy.
In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
Using your hands or a cookie scoop, portion out dough balls about 1 inch in diameter. If you like, roll each ball in sanding sugar to add a decorative touch and extra crunch.
Place the cookie dough balls on a parchment-lined baking sheet, spacing them about 2 inches apart. Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Once baked, remove the cookies from the oven and allow them to cool on the baking sheet for about 5 minutes before transferring them to a cooling rack. Enjoy!