Add the fermented dough mixture to the well and start kneading at a low speed, allowing the dough to come together. If the dough feels dry, gradually incorporate the remaining milk. The dough will be quite sticky at this stage.
Boost the kneading speed to 4-5 and continue for 5 minutes.
Gradually add the butter chunks, continuing to knead until the dough pulls away from the sides of the bowl, becoming smooth, shiny, and highly elastic.
Form a ball with the dough and cover it with cling film or a towel. Allow it to rest and rise for 1 to 1.5 hours, or until it doubles in volume.
Grease a 24 cm x 24 cm mold or line it with baking paper.
Punch down the risen dough to release any air, then divide it into 16 equal parts, each weighing about 70 g.
Place the dough pieces in the mold and let them rise again for 45 minutes, ensuring they expand to touch the mold’s edges.
Preheat the oven to 170°C (338°F).
Brush the risen dough with the egg yolk and milk mixture for a golden glaze.
Bake in the oven for 30 minutes or until the brioche turns a lovely golden brown.
Once baked, remove the brioche from the oven and transfer it to a wire rack to cool.
