Steps
1. Preheat your oven to 180°C (350°F) and line a baking sheet with parchment paper.
2. In a mixing bowl, cream together the softened butter and powdered sugar until light and fluffy.
3. Add the egg yolk and vanilla extract, mixing until well combined.
4. In another bowl, whisk together the flour, ground pistachios, baking powder, and salt.
5. Gradually add the dry ingredients to the wet mixture, stirring until a soft dough forms.
6. Using your hands, shape the dough into small balls and place them on the prepared baking sheet.
7. Press a whole pistachio into the center of each cookie.
8. Bake for 12-15 minutes, or until the edges are lightly golden.
9. Let the cookies cool on a wire rack before serving.