In another bowl, place the softened butter (let it sit at room temperature or gently soften in the microwave—do not melt). Add the sugar and beat with a mixer until the mixture is light and fluffy. Add the egg and vanilla extract, and beat a little more.

Add half of the flour, the baking powder, salt, and the walnut-sesame mixture. Mix to combine. Add the remaining flour and knead by hand. The dough will be soft and a little sticky. Wrap the dough in plastic wrap and place in the freezer for 15 minutes. Do not leave it longer.

Let the cookies cool completely before removing them from the baking sheet. Store them in a metal tin and enjoy with your coffee or tea!