01 -
Combine granulated sugar and water in a small saucepan. Stir over medium heat until the sugar is fully dissolved. Remove from the heat and set aside about one third of the syrup to cool for use. Let the remaining syrup cool and store in a clean container in the refrigerator for up to two weeks.
02 -
Preheat oven to 175°C. Line a baking sheet with parchment paper and set aside.
03 -
Place softened butter in a medium mixing bowl. Use an electric hand mixer to beat the butter until creamy. Add almond flour, powdered sugar, cocoa powder, and salt; mix until ingredients are well incorporated and form a paste. Add eggs one at a time, mixing thoroughly after each addition. Mix in almond or vanilla extract with the final egg. Transfer frangipane to a piping bag, if desired.
04 -
Slice each croissant in half lengthwise. Place bottom halves on the prepared baking sheet. Brush the cut side of each croissant half generously with the simple syrup using a pastry brush.
05 -
Pipe or spread a layer of chocolate frangipane onto each bottom half, reserving some frangipane for topping. Add a portion of dark chocolate pieces or chocolate chips onto the frangipane layer of each croissant. Place the top halves back on and gently press.
06 -
Pipe or spread a line of frangipane on the surface of each croissant. Press sliced almonds firmly onto the frangipane.
07 -
Bake for 22 to 25 minutes until croissants are golden brown and crisp. Allow to cool on the baking sheet placed over a wire rack for at least 10 minutes.
08 -
Using a fine mesh sieve, dust cooled croissants with powdered sugar. Serve warm or at room temperature.