Mix together ripe/active sourdough starter with all-purpose or bread flour and water. Cover loosely and let sit 10-12 hours at 78-80°F until doubled, bubbly & peaked.

To a large bowl, mix together ripe levain with water. Add the brown sugar, vanilla extract, salt and bread flour. Mix together using a dough whisk or spoon until a wet and sticky dough forms and the ingredients are fully combined. Cover and let rest for 30 minutes.

After the dough has rested, perform a series of 'stretch and folds' over the next 1 ½ hours. The goal is to strengthen the dough through a gentle kneading process.

After 30 minutes, perform your first set of stretch and folds. Cover the dough and let rest for 30 minutes.

After 30 minutes, grate the cold butter. Put half of the grated butter on top of the dough. Stretch and fold the dough again, incorporating the flakes of butter into the dough. Cover and let rest for 30 minutes.

30 minutes later, add the rest of the butter to the top of the dough. Stretch and fold again. Cover and let rest for 30 minutes.

Gently pull the dough into a 12 by 16 rectangle shape. Sprinkle about ⅔ of the chocolate chips over the entirety of the dough. Fold one side of the dough to the middle and then the other side of the dough to the middle. Add the remaining ⅓ of the chocolate chips on top of that dough. Then roll the dough up into a cylinder and place it back in the bowl.

Cover the dough and let rise for 6-7 more hours.

Tip the bowl upside down, allowing the dough to fall onto a clean counter surface. Be gentle to avoid degassing the dough.

Let the dough rest uncovered for about 30 minutes at room temperature.

Prepare a bowl or banneton. Place a kitchen towel or hair net in the bowl and liberally flour as needed. Sprinkle a little flour on top of the dough.

Cover the dough with the tea towel/shower cap/plastic wrap and refrigerate overnight or up to 12-18 hours.

Preheat a Dutch oven at 450°F for 20 minutes. Once preheated, pull the loaf out of the refrigerator. Remove the covering. Place a piece of parchment paper on top of the dough. Flip the dough over so it is now sitting on the parchment paper.

Use a very sharp knife or bread lame to score the dough.

Carefully remove the Dutch oven from the 450°F oven. Take the lid off and place your bread into the Dutch oven. Lower the temperature to 425°F and bake for 30 minutes. After 30 minutes, take the lid off the Dutch oven and continue baking for 15 minutes until the bread is baked through and reaches 195-200ºF temperature.

Remove the Dutch oven and let the bread cool on a baking rack.