1. In a bowl, using an electric mixer, mix together ground almonds, sugar, salt, diced butter, 1 egg, and almond extract, beating until the mixture is creamy. Refrigerate the almond cream for 30 to 60 minutes or until firm enough to hold in small mounds.
2. On a work surface, roll out a sheet of puff pastry into a 30 cm square, then cut it into 9 squares of 10 cm. Repeat with the other sheet of pastry. Using a spoon, place a mound of chilled almond cream in the center of half of the squares, about 2 tablespoons (30 ml) at a time (do not spread it). In a small bowl, beat the remaining egg. Using a brush, brush the edges of the filled squares with the beaten egg. Place one remaining pastry square on top of each filled square, making sure to press the edges with your fingers to seal them.
3. Place the squares on a baking sheet lined with parchment paper, spacing them apart. Using a fork, press the edges of the squares. Brush the tops of the pastries with beaten egg and sprinkle with sliced almonds.
4. Bake in a preheated oven at 200 °C for 20 to 25 minutes or until the pastries are golden and puffed. Place the baking sheet on a rack and sprinkle with powdered sugar. Let cool for 5 minutes. (The pastries can be stored for up to 5 days at room temperature or up to 1 month in the freezer.)
5. Variation
Almond and Chocolate Cream Puff Pastry
At step 2, lightly press the small mounds of almond cream, then sprinkle 80 ml of semi-sweet chocolate chips on top.