First, in a small bowl measure out the raisins and soak in warm to hot water.
In a large mixing bowl or the bowl of a stand mixer, measure out the sourdough starter, water, and brown sugar. Mix this up until the starter is dissolved in the water. Next, add the flours and with a spoon, Danish dough hook or the dough hook of the stand mixer, mix the dough until it is just combined. It will be a slightly shaggy dough. Let rest (fermentolyse) for 30 minutes.
After the 30 minutes, add to the large bowl, the raisins (drained well), butter, egg, cinnamon, and salt. Knead on low for 8-10 minutes.
NOTE: If the dough seems very wet you can add 30-40 grams flour or a ¼ cup to help it to come together well. The raisins add some moisture back into the dough so you might need a little more flour. Don’t add more than that though. The dough is fairly sticky, but you want it that way!
Transfer your dough to a tall sided container that will be easy to watch for when the bulk fermentation is done. I love using my 8-cup glass measuring cup, but a bowl could also work.
Cover with a bowl cover or tea towel and let rest for 30 minutes.
After the 30 minutes you can perform your first set of coil folds. Get your hands slightly wet and grab each side of the dough and pull the dough up. (The dough will stretch but you don’t want it to rip.) Complete this turning the dough a quarter turn for each fold.
Let the dough rest and do 2-3 more coil folds and rests.
After the coil folds are complete let the dough rest until bulk fermentation is complete.
NOTE: Bulk fermentation is basically the process of letting the dough rise. This is important to give you a fully well proofed loaf. It is always a little tricky. In my 72-degree kitchen it can take roughly 3-4 hours for the bulk ferment to be done. This varies based on the kitchen temperature. Shorter for if it is warmer, longer if it is cooler.
At 70-72 degrees I let the dough double in size before shaping it.