01 - Combine gluten-free flour, sugar, salt, and instant yeast in a large mixing bowl. Whisk warm milk and egg together, then pour into dry ingredients. Mix until soft dough forms, then beat in softened butter until fully incorporated. Cover bowl and refrigerate for 1 hour.
02 - Place cold butter between two sheets of parchment paper. Pound and roll into a rectangle approximately 5 x 7 inches (13 x 18 cm). Transfer to refrigerator until firm.
03 - Roll chilled dough on lightly floured surface into 10 x 14-inch rectangle. Place butter layer in center and fold dough over to encase completely. Roll gently back to 10 x 14 inches, then fold into thirds like a letter. Wrap and chill for 30 minutes.
04 - Repeat rolling and folding process two more times for a total of three folds, chilling 30 minutes between each fold. This creates the flaky layers essential for proper croissants.
05 - Roll dough into 12 x 16-inch rectangle. Cut into 8 equal triangles. Starting from wide end, roll each triangle into croissant shape. Place shaped croissants on parchment-lined baking sheet, leaving space for expansion.
06 - Cover loosely and let rise in warm place for approximately 2 hours until puffy and doubled in size. Preheat oven to 400°F. Whisk egg yolk with milk for glaze and brush over risen croissants. Bake for 18-20 minutes until deep golden brown.
07 - Transfer croissants to wire rack and cool completely before serving to preserve internal texture.