Proof yeast: heat milk in a small sauce pan until lukewarm. Transfer to a bowl and add yeast. Let sit for 10 minutes until bubbly and foamy.
Meanwhile, combine flour; sugar and salt in the bowl of your stand mixer fitted with the paddle attachment.
Add the cubed butter and process until it is fully incorporated.
Switch the paddle attachment for a dough hook and stir in the proofed yeast.
Add the egg lightly beaten along with the vanilla extract. Knead on medium speed for 7-8 minutes until the dough.
Cover the bowl and let rise for 3 hours until tripled in size.
To shape
Prepare a loaf pan (9 x 5 inches) by tearing a sheet of parchment paper large enough so that there is overhang on the two long edges. This will make it easier to lift the baked bread out of the pan. Grease the sides of the pan not covered by the parchment paper.
Use a rolling pin to flatten the dough on a lightly floured surface to create a rectangle approximately 12 x 18 inches.
Brush half the melted butter over the entire surface. Cover the surface with chocolate chips. Roll the dough tighlty from one of the longerr edges.
Slice the roll in half lengthwise exposing the chocolate chip filling but leave the top part of attached. Twist the two pieces of dough together.
Don't worry if it is not perfect or if chocolate chips fall out during the process. You can top the final shaped bread with those scattered chocolate chips.
You will notice at this point that the dough is much longer than your loaf pan! Simply tuck the two ends of the twisted dough underneath, carefully lift the dough and place in the prepared loaf pan.
Cover and let rise one more hour.
Preheat oven to 350 degrees F. Brush the remaining melted butter over the bread and sprinkle with salt flakes (if using). Bake for 25-30 minutes until the loaf is golden brown.
Transfer to a wire rack and let cool before slicing.
Notes
Substitutions and Variations-Try replacing half the chocolate chips with slivered almonds or chopped pistachios. -This recipe works well with non dairy milk options. -Although I have not tried it, it should work well with non dairy butter.StorageKeep well wrapped, at room temperature, for up to 3 days.To FreezeWrap well and freeze for up to 1 month. Defrost at room temperature.Can the brioche bread be prepared in advance?Yes it can! You can refrigerate the dough, after the first rising, overnight. Let it come to room temperature, 2-3 hours, the following day before shaping it. You may also refrigerate the shaped chocolate chip bread and bake it the following day. Bring it to room temperature, brush with melted butter and bake.