1. Begin by preparing the almond cream. In a bowl, combine almond flour, sugar, and butter until well mixed. Add eggs and continue blending until smooth. Optionally, include a dash of almond extract for enhanced flavor.
2. Prepare the sugar syrup by heating sugar and water in a saucepan until the sugar dissolves. For depth, add orange blossom water or a splash of dark rum.
3. Cut each day-old croissant in half horizontally. Lightly brush the cut sides with the sugar syrup.
4. Spread a generous layer of almond cream on one half of the croissant, ensuring even coverage. Place pieces of dark chocolate on top of the almond cream.
5. Place the top half of the croissant back on the filled half. Spread a thin layer of almond cream over the surface of the croissant. Sprinkle sliced almonds on top.
6. Preheat the oven to 350°F (180°C). Arrange the croissants on a baking sheet with sufficient spacing, and bake for 12-15 minutes until golden and crispy.
7. Allow the croissants to cool slightly before serving to enjoy their full flavor and texture.