Brioche dough

1. Warm the milk until lukewarm. If using active dry yeast, stir it into the milk and let stand 5–10 minutes until foamy.
2. In the bowl of a stand mixer fitted with the dough hook, combine the flour, granulated sugar, and salt.
3. Add the egg yolks, then pour in the milk with the yeast.
4. Mix on low speed, then increase to medium and knead for 5–7 minutes until a smooth dough forms and pulls away from the sides of the bowl.
5. With the mixer running on low speed, add the melted and cooled butter.
6. Continue kneading for 2–3 minutes until the butter is fully incorporated and the dough is elastic and smooth. Shape into a ball, cover, and let rise in a warm place for 1½ to 2 hours, until doubled in size.
7. Punch down the dough to release the air and transfer to a lightly floured surface.
8. Divide into 4 equal pieces and shape into balls.
9. Roll each ball into a thin 10-inch (25 cm) circle, placing them on parchment paper.

Chocolate filling

1. In a bowl, combine the chopped chocolate, softened butter, brown sugar, and cocoa powder.
2. Melt in the microwave in short bursts, stirring between each, until smooth.
3. Let cool slightly so the filling thickens.

Assembly

1. Place the first dough circle on a baking sheet lined with parchment paper.
2. Spread an even layer of chocolate filling over the surface, leaving a small border.
3. Top with a second circle and repeat. Add the third circle and filling, then finish with the fourth circle on top (no filling on top).
4. Place a plate or cake ring over the dough and trim the edges to form a neat 10-inch (25 cm) circle.
5. Gently press a small glass into the center to mark it.
6. Using a sharp knife or pizza cutter, cut the dough into 4 sections, stopping at the center mark.
7. Cut each section in half, then again to make 16 strips.
8. Take two adjacent strips, twist one away from you twice and the other toward you twice, then pinch the ends together firmly.
9. Repeat all around to form a star shape.
10. Cover loosely and let rise for 30–60 minutes, until slightly puffy.

Baking

1. Preheat the oven to 347°F (175°C). Brush the dough gently with the remaining egg white.
2. Bake for 18–22 minutes, until puffed and deep golden brown.
3. If it browns too quickly, cover loosely with foil.
4. Let cool for 10–15 minutes, dust with powdered sugar, and serve.