Soak the raisins in water prior to starting the dough.
Combine the flour, active starter, butter, salt, sugar, vanilla, and water in bowl of the stand mixer. Using the paddle attachment or the dough hook, knead the dough on low speed until it is stretchy, about 5-10 minutes with the stand mixer.
Strain the raisins and add them to the dough. You can do this by adding them to the dough and turning the mixer on low until they are mixed in or you can knead by hand just enough to make sure that all the raisins have been fully incorporated.
Remove the dough from the mixer and roll it into a tight ball.
At this point the dough can be transferred to a glass bowl or a ceramic bowl for the bulk fermentation, or for best results, you can proceed to the following recommendation of two stretch and folds which will help with gluten development and lift your bread creating an amazing crumb.
Stretch and Fold (OPTIONAL)
Begin the first set of stretch and folds about 30 minutes into the bulk rise followed by another set 30 minutes later (2 sets total). Perform the stretch and folds by grabbing the right side of the dough, stretching it out and laying it across the center to the left side. Rotate your bowl 15 degrees, and stretch out the right side again, placing it to the left. Repeat this two more times. Then prepare the dough for the first rise.
Place the dough smooth side up in a glass bowl greased with olive oil. Cover the dough with a damp towel, plastic wrap, or a tight fitted bowl cover, and let it rise overnight, or at least eight hours in a warm place on your countertop.