In a large mixing bowl, stir together flours and water with your hands until well combined. Cover and set aside in a warm part of your kitchen, ideally 78°, for at least 1 hour, up to 3 hours.
Mix: Using your hands, add salt, sugar, vanilla and starter to your dough mixing until well combined.
Continue to work the dough by hand, using a shoveling motion to lift dough from the bottom up and falling over itself for a few mins. Let rest 30 mins.
Now do your first stretch and fold. Do a total of 4 every 30 minutes. On the third stretch and fold incorporate the 1/4 c. sprinkles.
Once dough has nearly doubled, shape into a ball and rest 30 mins.
For the final fold, I add some more sprinkles (eyeball it)-shape and place into floured banneton.
Chill a few hours or overnight.
Bake at 450 covered 20 mins (475 tends to burn the sprinkles)
Uncover and bake 15-25 more mins until 205 degrees inside.