Preheat the oven to 180°C (350°F) and line a baking sheet with parchment paper.

Cream the butter and sugar together until light and fluffy.

Add the vanilla extract and egg yolk, mixing well to combine.

Sift in the flour, baking powder, and salt, then mix until a soft dough forms.

Roll the dough into small balls and place them on the prepared baking sheet, spacing them slightly apart.

Flatten each ball gently with the back of a spoon.

Bake for 8-10 minutes or until the edges are lightly golden.

Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.