01 - Whisk together gluten-free flour, almond flour, sugar, yeast, and salt in a large bowl until thoroughly combined.
02 - In a separate bowl, combine warm milk, warm water, egg, and softened butter. Pour the wet mixture into the dry ingredients and mix until a sticky dough forms.
03 - Shape the dough into a rectangle, wrap tightly in plastic wrap, and refrigerate for 45 minutes to firm up.
04 - Slice cold butter into thin slabs. Place between parchment paper sheets and pound or roll into an even 6 x 8-inch rectangle. Chill if butter becomes too soft.
05 - Roll chilled dough on a lightly floured surface into a 12 x 8-inch rectangle. Place butter layer over bottom two-thirds of dough, leaving a border. Fold top third down over butter, then fold bottom third up like a letter.
06 - Rotate dough 90 degrees, roll to 12 x 8-inch rectangle, and fold again. Repeat rolling and folding 2 more times, chilling for 20 minutes between each turn.
07 - After the final fold, wrap dough and refrigerate for 1 hour to relax gluten-free flour and ensure clean layers.
08 - Roll chilled dough into a 16 x 10-inch rectangle. Using a sharp knife or pizza cutter, cut into 8 triangles. Roll each triangle tightly from wide end to point, forming crescent shapes.
09 - Place croissants point-side down on parchment-lined baking tray. Cover loosely and let rise in a warm place for 1 to 1 1/2 hours until slightly puffy.
10 - Preheat oven to 400°F.
11 - Whisk egg and milk together until smooth. Brush croissants lightly with egg wash, avoiding excess that can inhibit rise.
12 - Bake for 20 to 22 minutes until deep golden brown and flaky. Cool slightly on the baking tray before serving.