In order to make this recipe, you will need to feed your starter. Give it time to become bubbly and active. This usually takes between 4-6 hours.
In the bowl of a stand mixer, add all of your ingredients except the chocolate chips. Yes all of them. There’s really no need to add them separately. Just make sure that your milk and butter are at room temperature.
Using the dough hook attachment, knead the dough on low speed until smooth and elastic. This will likely take 10-15 minutes. Because this is an enriched brioche dough, it will be very sticky. Resist the urge to add more flour.
Gently pull the dough up and see if you can stretch it out so much that you can almost see through it. This is called the windowpane test and is a good way to see if your dough needs more kneading to form the gluten structure. You can also mix the dough by hand, just know that this will take longer and a lot of arm muscle. Transfer your dough to a lightly greased bowl.
Cover the bowl with plastic wrap and place it in a warm spot for 6-8 hours. Do not rush this part. Let your dough rise and double in size or very close to it.
Once the dough has risen, be sure the bowl is covered tightly and place it in the refrigorator overnight for best results ora minimum of 4 hours.
After the cold proof, your dough will be stiff. Use a bowl scraper to pull the dough away from the sides of the bowl and out onto a lightly floured surface.
Now you will add the chocolate chips. Gently fold the chips into the dough by folding over the sides like an envelope.Then divide the dough into 2 equal portions and shape them into a tight ball.
Place each ball into a 9x5-inch loaf pan, cover once again with plastic wrap and let the brioche loaves rise in a warm place until they double in size. This may take 4-8 hours depending on the temperature of the room.
Preheat the oven to 400°F and brush the tops of the loaves with an egg wash. An egg wash is simply combining an egg yolk and 1 tablespoon of water in a small bowl.
Bake for 25-30 minutes until the tops are golden brown.
Once baked, be sure to cool before slicing. I like to remove my loaves from the pan fairly quickly and place them on a cooling rack.