01 - Whisk together gluten-free flour, almond flour, sugar, yeast, and salt in a large bowl until thoroughly combined.
02 - Combine warm milk, warm water, egg, and softened butter in a separate bowl. Pour into dry ingredients and mix until a sticky dough forms.
03 - Shape dough into a rectangle, wrap tightly in plastic wrap, and refrigerate for 45 minutes to firm.
04 - Slice cold butter into thin slabs. Place between parchment paper sheets and pound or roll into an even 6 x 8-inch rectangle. Refrigerate if soft.
05 - Roll chilled dough into a 12 x 8-inch rectangle on lightly floured surface. Position butter layer over bottom two-thirds, leaving 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 - Wrap laminated dough and refrigerate for 1 hour to relax gluten-free structure.
08 - Roll dough into 16 x 10-inch rectangle. Cut into 8 equal triangles using sharp knife or pizza cutter. Roll each triangle tightly from wide end to point. Place on parchment-lined baking tray, point side down.
09 - Cover loosely and let rise in warm place for 1 to 1.5 hours until slightly puffy and increased in volume.
10 - Heat oven to 400°F.
11 - Whisk egg with milk. Brush croissants lightly with wash, avoiding pooling in crevices.
12 - Bake for 20 to 22 minutes until deep golden brown and cooked through. Cool briefly before serving.