Combine almond flour and cold, cubed butter in a mixing bowl. Use a pastry cutter or your fingertips to blend until mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.
Add a beaten egg to the flour mixture and quickly knead until a cohesive dough forms. Shape into a flat disk, wrap with plastic wrap, and refrigerate for 10-15 minutes to firm up.
On a lightly floured surface, roll out the chilled dough into a rectangle about 1/8 inch thick. Fold the dough into thirds like a letter, then rotate 90 degrees and repeat the rolling and folding process to create layers.
Refrigerate the folded dough for another 10 minutes to relax the gluten and keep layers distinct. Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
Roll out the layered dough into a thin rectangle again and cut into triangles. Roll each triangle from the wide end to the tip to form croissant shapes. Place them on the prepared baking sheet.
Beat the remaining egg to make an egg wash, then brush it generously over the croissants' surfaces. Bake for 15-20 minutes until golden brown and crispy. Remove from oven and let cool slightly before serving.
