Mix sweet levain ingredients together in a jar

Cover and rest at room temperature for 12 hours until doubled in size

In a bowl cream together softened butter brown sugar and powdered sugar until light

Mix in sourdough starter and vanilla extract until well combined

In a separate bowl whisk together flour cornstarch salt and baking soda

Gradually add dry ingredients to wet ingredients mixing until just combined

Fold in mini chocolate chips

The mixture should be thick but spreadable like thick frosting

If too thick add 1 teaspoon milk if too thin add 1 tablespoon flour

Cover and refrigerate for cold fermentation 12 plus hours

Mix freshly brewed coffee and cocoa powder together

Cover and let bloom for 1 hour

In a large mixing bowl combine sweet levain bloomed chocolate water sugar and flour

Mix until just combined and let rest for 30 minutes

Add salt and vanilla extract to the dough

Mix thoroughly and let rest for another 30 minutes

Fold in chocolate chips distributing evenly throughout the dough

Let rest for 30 minutes

Begin stretch and folds every 30 minutes for 2 hours total 4 sets of folds

After the final fold let the dough rest at room temperature for 6 to 8 hours until it has increased in size by about 50 percent

Checking for signs of proper fermentation is more important than following a clock

Shaping with Cookie Swirl and Final Proof 5:30 PM

After bulk fermentation is complete gently stretch the entire dough out into a rectangle approximately 10 inches by 17 inches

Divide the cookie swirl filling in half

Place a cookie swirl portion between two pieces of parchment paper. Roll out the first half into a rough rectangle about 10 inches long and 5 to 6 inches wide and lay it in the middle of the dough rectangle

Fold each side of the dough up into the middle covering the cookie swirl layer

Take the remaining half of the cookie swirl filling place between the same parchment paper and roll it out in a rough rectangle approximately 10 inches long and about 5 inches wide then lay it on top of the folded dough

Gently roll the dough from one edge to the other creating a spiral with the cookie swirl throughout

Place the shaped loaf seam side up in a large proofing basket or bowl lined with floured cloth

Cover and refrigerate overnight 12 to 16 hours

Preheat oven to 450 degrees F (230 degrees C)

Remove cover and place a piece of parchment over top of the proofing container

With one hand on top and one hand on the bottom of the proofing container flip it over and put the loaf onto the parchment

Place the loaf inside of your baking pan, I used large USA bread pans

Cover with a second bread pan

Bake for 9 minutes covered

Remove the lid and score your bread. Replace the lid and bake an additional 40 minutes

Remove the lid and bake an additional 10 to 15 minutes internal temperature needs to reach 200 degrees F

Cool completely on a wire rack before slicing at least 2 hours