Instructions:
- Activate Yeast: Warm the milk slightly. In the mixer bowl, combine milk, yeast, and a pinch of sugar. Let stand for 5–10 minutes until foamy.
- Form Initial Dough: Whisk together flour, remaining sugar, and salt. Add eggs to the yeast mixture. Gradually add the flour mixture and mix on low speed until a shaggy dough forms.
- Develop Gluten: Increase mixer speed to medium-low and knead for 5 minutes until the dough begins to smooth out.
- Incorporate Butter: With the mixer on low, add the cold butter cubes one at a time, waiting until each cube is mostly incorporated before adding the next (this may take 5–10 minutes).
- Final Knead: Increase speed to medium and knead until the dough passes the 'windowpane test' (it stretches thin enough to see light through without tearing). This will take another 10–15 minutes.
- First Rise (Bulk Fermentation): Place dough in a lightly oiled bowl, cover, and let rise in a warm spot until doubled (approx. 1.5–2 hours).
- Chill: Gently deflate the dough, wrap tightly, and chill in the refrigerator for at least 2 hours, or ideally overnight. This chilling step is crucial for easy handling.
- Shape the Nest: Divide the chilled dough into three equal pieces. Roll each piece into a long rope, about 20–24 inches long. Braid the three ropes into a tight, three-strand braid. Pinch the ends securely. Carefully form the braid into a circle (the nest shape), overlapping the ends slightly to seal.
- Second Proof (Final Rise): Place the nest on a baking sheet lined with parchment paper. Cover loosely and let rise in a warm spot for 45–60 minutes until puffy.
- Bake Preparation: Preheat oven to 375°F (190°C). Gently brush the entire nest with the prepared egg yolk wash. Sprinkle lightly with sugar, if desired.
- Bake: Bake for 30–35 minutes, rotating halfway through, until deep golden brown and the internal temperature reaches 200°F (93°C).
- Cool: Transfer the brioche nest to a wire rack to cool completely before filling.