Prepare the Filling: In a medium bowl, combine the softened butter, powdered sugar, almond flour, egg, almond extract, and vanilla extract. Mix everything together until it forms a smooth, creamy paste.
Thaw the Pastry: Take your gluten-free puff pastry out of the freezer and let it thaw according to the package directions.
Preheat & Prep: Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper.
Cut the Pastry: Once the puff pastry is thawed, gently unfold it on a lightly floured surface (use gluten-free flour!). Cut the pastry into large triangles.
Fill the Croissants: Place a spoonful of the almond filling at the wide end of each triangle.
Roll the Croissants: Starting at the wide end, carefully roll each triangle towards the point, forming a crescent shape. Gently curve the ends inward to create that classic croissant look.
Egg Wash: In a small bowl, whisk together the remaining egg and the tablespoon of milk or cream. Brush the tops of the croissants with this egg wash.
Add Almonds: Sprinkle the sliced almonds over the egg-washed croissants.
Bake: Place the croissants on the prepared baking sheet, leaving some space between them. Bake for 18-22 minutes, or until they are golden brown and puffed up.
Cool & Enjoy: Remove the croissants from the oven and let them cool slightly on the baking sheet before transferring them to a wire rack. They're best enjoyed warm!