01 - Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper and set aside.
02 - In a large mixing bowl, cream the softened butter and granulated sugar together using an electric mixer until the mixture becomes light and fluffy, approximately 3 minutes.
03 - Add the egg and vanilla extract to the creamed butter mixture. Beat until fully combined and smooth.
04 - In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add the dry ingredients to the butter mixture, mixing on low speed until a soft dough forms. Cover and chill the dough while preparing the almond filling.
05 - In a small bowl, combine the finely ground almonds, granulated sugar, egg, softened butter, almond extract, and a pinch of salt. Mix thoroughly until a thick, spreadable paste forms.
06 - Scoop approximately 1 tablespoon of chilled dough and flatten it in the palm of your hand. Place ½ teaspoon of almond filling in the center, then fold the dough around the filling, gently shaping it into a crescent to resemble a miniature croissant.
07 - Arrange the shaped cookies on the prepared baking sheets, spacing them about 2 inches apart. Gently press sliced almonds onto the surface of each cookie.
08 - Bake for 13 to 15 minutes, or until the edges are golden brown. Allow the cookies to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.
09 - Once the cookies have cooled completely, generously dust with powdered sugar before serving.