**Make the Simple Syrup:** In a pot over medium heat, combine water, sugar, and almond extract. Bring to a boil until the sugar dissolves, then simmer for 10 minutes. Transfer to a bowl and let it cool to room temperature to thicken.
**Prepare the Almond Filling:** In a bowl, mix almond flour, sugar, salt, unsalted butter, vanilla extract, almond extract, eggs, and heavy cream until light and fluffy using a stand or hand mixer.
**Assemble and Bake:** Preheat oven to 350°F. Slice the croissants in half and soak both sides in the almond syrup generously. Spread almond filling and chocolate on one side, then close the croissant. Add a line of almond filling on top and sprinkle with sliced almonds. Repeat for the rest of the croissants.
**Bake:** Bake in the oven for 12 to 15 minutes until crispy all around. Let them cool for 15 minutes before enjoying!