01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer until pale, light, and fluffy—about 3 minutes. Add the egg and vanilla extract, mixing until fully incorporated.
03 - 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, cohesive dough forms. Cover and chill the dough while preparing the filling.
04 - In a small bowl, combine the finely ground almonds, granulated sugar, egg, softened butter, almond extract, and a pinch of salt. Stir until a thick, spreadable paste forms.
05 - Scoop approximately 1 tablespoon of chilled dough and flatten it in the palm of your hand. Place ½ teaspoon of the almond filling in the center, then fold the dough around it, gently shaping it into a crescent to resemble a mini croissant. Place on the prepared baking sheets, seam side down.
06 - Gently press sliced almonds onto the top of each shaped cookie, pressing lightly so they adhere to the surface.
07 - Bake for 13 to 15 minutes, rotating the sheets halfway through, until the edges are a warm golden brown. Let the cookies rest on the baking sheets for 5 minutes before transferring to a wire cooling rack.
08 - Allow the cookies to cool completely on the wire rack. Dust generously with powdered sugar just before serving.