Activate the Yeast: In a small bowl, combine warm milk (110°F) and sugar. Sprinkle yeast over the mixture and let it sit for 5-10 minutes until frothy.
Make the Dough: In a large mixing bowl or stand mixer, combine flour and salt. Add the yeast mixture, softened butter, and eggs. Mix on low speed until combined, then knead for 8-10 minutes until smooth and elastic.
First Rise: Place the dough in a greased bowl, cover, and let it rise in a warm place for 1-2 hours, or until doubled in size.
Add Chocolate Chips: Punch down the dough and gently knead in the chocolate chips until evenly distributed.
Braid the Dough: Divide the dough into 3 equal pieces. Roll each piece into a 12-14 inch rope. Braid the ropes together and pinch the ends to seal.
Second Rise: Place the braided dough on a parchment-lined baking sheet, cover, and let it rise for 30-45 minutes.
Preheat Oven: Preheat the oven to 190°C (375°F).
Egg Wash: Whisk together 1 egg and 1 tbsp milk. Brush lightly over the braided dough.
Bake: Bake for 25-30 minutes, or until golden brown and hollow-sounding when tapped.
Cool and Serve: Let the brioche cool on a wire rack for 15 minutes before slicing.