01 - Whisk together gluten-free flour, almond flour, sugar, yeast, and salt in a large bowl until thoroughly combined.
02 - Mix warm milk, warm water, egg, and softened butter in a separate bowl. Pour wet mixture into dry ingredients and stir until a sticky dough forms.
03 - Shape dough into a rectangle, wrap tightly in plastic wrap, and refrigerate for 45 minutes to relax gluten-free flours.
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 lightly floured surface into 12 x 8-inch rectangle. Position butter layer over bottom two-thirds of dough, leaving border. Fold top third down over butter, then fold bottom third up (letter fold).
06 - Rotate dough 90 degrees, roll to 12 x 8-inch rectangle, and fold as before. Repeat rolling and folding 2 more times, chilling for 20 minutes between each turn.
07 - Wrap dough and refrigerate for 1 hour after final fold to firm butter layers.
08 - Roll dough into 16 x 10-inch rectangle. Cut into 8 equal triangles using sharp knife or pizza cutter. Starting from wide end, roll each triangle tightly into crescent shape. Place point-side down on parchment-lined baking sheet.
09 - Cover loosely and let rise in warm place for 1 to 1 1/2 hours until slightly puffy and expanded.
10 - Preheat oven to 400°F. Whisk egg and milk for egg wash. Brush croissants lightly with mixture.
11 - Bake for 20 to 22 minutes until deep golden brown and flaky. Cool slightly on baking sheet before serving.