My Oakland Sourdough (yields one 2 lb loaf):
For the liquid levain:
16-18 hours before combining with dough mix
20g active culture
85g bread flour
After removing the 190g for the loaf, you will have 20g leftover for the next build.
Final Dough: 190g liquid levain (125% hydration)
300g bread flour
150g whole wheat flour
260g h2o @ about 78 degrees F
10g salt (reserved)
Combine all flours, levain and water in a mixing bowl and mix on low speed (speed #2 on a Kitchenaid stand mixer) for two minutes or just all ingredients are incorporated and mix is 'shaggy'. Autolyse, or let sit, for fourty five minutes. Add salt and mix on medium high speed (speed #4 on a Kitchenaid stand mixer) for 3 minutes if using a stand mixer. If mixing by hand, do a series of stretch and folds. What you're looking for is the dough to start to form a ball and have a soft, glossy sheen to it and a good amount of strength, but not extremely stiff. Add seeds at the very end and mix lightly on low speed so as not to tear the gluten. Remove dough from bowl and place on a nonporous counter top.
After 45 minutes, do a series of stretch and folds and rough shape into a ball. Let rest 45 minutes and repeat. After another 45 minutes, do a pre-shape into a round (or divide and make baguettes if you want). Let rest for 20 minutes and shape the loaf to your final desired shape. Place seam side down on an oiled sheet of parchment cut to be about twice the size of the shaped loaf. I like to also lightly flour the bottom of my loaf to insure against sticking. Lightly mist the top with oil or dust with flour and cover with plastic wrap. At this point you can refrigerate overnight or proof and bake in 3-4 hours. Either way will yield great results. If you choose to retard overnight, remove the dough 3 hours before baking. All these times are based on a room temperature of about 71 degrees F.
For the bake, preheat oven with a baking stone if you have it to 480 degrees for one hour before you are ready to load. There are many options for steaming a home oven, I use an old milk frother wand fed into my oven from a broken espresso machine. Or you can do the dutch oven trick. You'll want a good amount of steam for at least the first 15 minutes for a good grigne, or ear, to develop. Remove the plastic wrap from the loaf about 20 minutes prior to let it dry out a bit. You want it just dry enough that it will not stick to the knife when you score. You can also lightly flour the top to ensure a clean cut. I prefer it without.
When your oven is preheated and you are ready to load the bread, you can go ahead and score the loaf. Make sure whatever steaming method you have devised is ready to go. Slip the loaf onto the baking stone, parchment and all, steam the oven and close it up quickly so as not to let moisture escape. If you're doing the dutch oven trick use the parchment as a sling and gently lower the loaf into the vessel being careful not to burn yourself. Decrease temperature to 475 and bake for 15 minutes with steam. After the first 15 minutes, rotate the loaf and reduce the temperature to 465. Check the loaf at the 35 minute mark for doneness, and if desired return the loaf for 5-10 minutes longer and rotate.
The finished loaf should have a dark brown but not quite black crust, a well-defined ear and should feel light for how large it is due to the open crumb structure. You can lower your baking temperature if you want a lighter golden brown.