Day 1: Feed your sourdough starter 6 to 10 hours before making the dough.

In a large bowl, mix the dry ingredients: flour, sugar and salt.

Add melted butter, milk, eggs and sourdough starter. Start mixing it with a spoon, then switch to your hands and knead it only until the dough is formed and no dry spots remain. The dough will feel sticky. Cover with a damp towel or plastic/beeswax wrap.

Let dough rise for 4 hours in a warm spot. Perform a stretch and fold every 30 minutes. You can wet your hands before handling the dough to make it easier. Always cover the dough between stretch and folds. It’s ready for cold fermentation when it has risen half its size.

Place dough inside fridge, covering it with plastic/beeswax wrap so it won’t develop a skin. Choose between 10 to 48 hours of cold fermentation.

Day 2: Take dough out of the fridge and leave it resting at room temperature for 1 hour.

Line a loaf pan with parchment paper.

Flour lightly the surface you’ll use to work the dough. Divide the dough into 4 equal pieces. Shape each piece, folding the dough over itself until getting a tight ball. Arrange shaped dough into the lined loaf pan.

Let shaped dough rise for 2 to 4 hours more in a warm spot, covering it loosely with plastic/beeswax wrap. It will be ready when dough reaches almost twice its initial size and feels soft and light to the touch.

Preheat oven for 20 minutes before baking, 350°F.

In a small bowl, separate one egg yolk for the egg wash. With a brush, cover brioche lightly with the egg wash just before baking.

Bake at 350°F for 45 minutes, or until brioche has a deep golden-brown color, sound hollow when tapped and reaches an internal central temperature of 190°F. If it’s browning too much on the top, cover with foil paper and continue baking.

Remove from pan and leave brioche loaf cooling on a cooling rack for 1 to 3 hours.