01 - Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
02 - In a large bowl, cream together the butter and granulated sugar until light and fluffy.
03 - Mix in the egg yolk and vanilla extract until combined.
04 - Add flour and salt; mix until a soft dough forms. Cover and chill for 15 minutes.
05 - Meanwhile, prepare the almond filling: In a medium bowl, combine almond flour, sugar, egg white, and almond extract. Stir until smooth and thick.
06 - Divide the chilled dough into 24 equal portions. Roll each into a ball, then flatten into a 2-inch (5 cm) round.
07 - Place 1/2 tsp of almond filling in the center of each round. Fold and pinch the dough around the filling to seal, shaping each into a crescent (croissant) shape.
08 - Gently press each crescent into the sliced almonds so they adhere on top.
09 - Place cookies on the prepared baking sheets, spacing them about 1 inch (2.5 cm) apart.
10 - Bake for 13–15 minutes, until edges are golden brown.
11 - Cool on the baking sheet for 5 minutes, then transfer to a wire rack.
12 - Once completely cool, dust cookies lightly with powdered sugar.