These gorgeous croissants are made with traditional dough and chocolate dough layered together. The final result is a marbled, slightly sweet, flaky masterpiece! Omit the glaze to serve them with savoury accompaniments.
To the first bowl, add the rest of the flour, salt, and milk to the risen sponge mixture (for the white dough). Stir to combine, and then knead by hand or with an electric mixer until strong, about 10 minutes. Cover with plastic wrap or a damp tea towel and allow to rise for 30 minutes.
To the second bowl, add the rest of the flour, cocoa, salt, sugar, and milk to the risen sponge mixture (for the chocolate dough). Stir to combine, and then knead by hand or with an electric mixer until strong, about 10 minutes. Cover with plastic wrap or a damp tea towel and allow to rise for 30 minutes.
Repeat the last process again; roll into a rectangle, fold into an envelope, rotate, roll, and fold again (for a total of 4 roll and folds with the butter inside). Wrap the folded piece of dough in plastic and refrigerate for 20-30 minutes.
Combine the glaze ingredients in a small mixing bowl and stir until very smooth. Brush or drizzle over warm croissants.
*The butter must be unsalted for best results.
Note: 1 cup of butter is exactly 1/2 of a 1-lb brick.