In a bowl, combine the ripe sourdough starter with the all-purpose or bread flour and water. Cover it loosely and let it sit for 10-12 hours at a temperature of 78-80°F until it has doubled in size and is bubbly.

In a large bowl, mix the ripe levain with water. Add the brown sugar, vanilla extract, salt, and bread flour. Stir with a dough whisk or spoon until a wet and sticky dough forms and all ingredients are well combined. Cover and let it rest for 30 minutes.

After resting, perform a series of stretch and folds over the next 1.5 hours to strengthen the dough. Wet your hand to prevent sticking, then reach under the dough, pull it up, and fold it over itself. Rotate the bowl a quarter turn and repeat this process. Cover and let it rest for 30 minutes between each stretch and fold.

For the first stretch and fold, after 30 minutes, cover the dough and let it rest for another 30 minutes.

For the second stretch and fold, grate half of the cold butter and place it on top of the dough. Keep the other half in the refrigerator until the next fold. Incorporate the butter into the dough and cover it again for another 30 minutes.

For the third stretch and fold, add the remaining butter to the dough and stretch and fold again. Cover and let it rest for 30 minutes.

After the final rest, transfer the dough to a clean surface and gently shape it into a rectangle measuring 12 by 16 inches. Sprinkle about two-thirds of the chocolate chips over the dough. Fold one side of the dough to the center, then fold the other side over it. Add the remaining chocolate chips on top and roll the dough into a cylinder. Place it back in the bowl.

Cover the dough and let it rise for 6-7 hours. It is ready to shape when it has risen about 70% and shows bubbles on the surface.

Gently tip the bowl upside down to let the dough fall onto a clean counter. Wet your hands and use a bench knife to tuck the dough under itself, creating tension. Repeat this process until you have a ball of dough.

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

Prepare a bowl or banneton by lining it with a kitchen towel and flouring it. Sprinkle some flour on top of the dough, then gently flip it so the floured side is down. Pull the dough towards you and fold it up, repeating this process around the dough to increase tension. Place the shaped dough into the prepared bowl.

Cover the dough with a towel or plastic wrap and refrigerate it overnight or for 12-18 hours. If you want to bake the same day, let it rise for 2-3 hours until puffed, then chill it in the refrigerator for an hour or two.

Preheat your oven to 450°F with a Dutch oven inside for 20 minutes. Once preheated, remove the dough from the refrigerator, cover it with parchment paper, and flip it onto the parchment.

Score the dough with a sharp knife at a shallow angle, about 1 inch deep.

Carefully take the Dutch oven out of the oven, remove the lid, and place the dough inside (with the parchment). Cover it with the lid and lower the oven temperature to 425°F. Bake for 30 minutes.

After 30 minutes, remove the lid and continue baking for an additional 15 minutes until the bread is fully baked and reaches an internal temperature of 195-200°F. Let the bread cool on a rack before enjoying.