Mix levain ingredients, cover loosely, and rest in a warm area (70-80℉) for 4 hours. I start the oven at 350F for a minute then stop it and put the mix in the oven.
When time is up, mix together your bread flour and whole wheat flour. Add 580g of your water to the flour mixture (hint there should be 100g left in the cup for mixing later). Mix just until your dough comes together with no more flour clumps. Cover with plastic wrap and let it rest next to his buddy in the oven for 1 hour.
Mix your remaining water with the salt until it’s well combined.
Mix your dough and levain together using about half the water to help incorporate. With your fingers, you can “poke” holes in the dough, this helps mixes everything together. Rest 20 minutes.
Doesn’t look pretty but don’t worry, that’s normal
Add the remaining water and add it to the mix. Again “poking hole” helps with mixing.
Use the “Slap and fold” for 2-4 minutes or until your dough is smooth and begins to catch some air. This is the same technique as for the pizza with Biga. For the slap and fold technique, pick up the dough in the middle of it from each side, and “throw” it from one end then fold. See this video Rest 15 minutes in the same warm area you placed your starter.
Now we need to do a series of stretch and fold. For this type of bread I find that 6 sets work better due to the high hydration.
-4 stretch and fold sets spaced by 30 mins restor-6 sets, first 4 spaced by 15 minutes, then 30 minutes rest for the next 2.Ex:13h45 stretch and fold14h00 stretch and fold14h15 stretch and fold14h30 stretch and fold15h00 stretch and fold15h30 stretch and fold Your dough should look somewhat like this after the third or fourth fold
Make sure to cover and place your dough back in the warm area after each fold.
Let your dough rest for 90 minutes
Stretch and fold is done by grabbing each “side” at a time and bringing it to the center.Example: take the right side of the dough and stretch it in the air ( DONT break the dough) then fold it in the center. Repeat for each side. See this video On an unfloured surface, dump out and divide your dough into 2 “even” pieces. It’s much easier if you use a dough cutter, just wet it first else it will stick. Preshape each piece into a light boule using the dough cutter doing a gentle circular motion ( you basically want to bring it into somewhat the shape of a ball), you should only swirl it on the countertop in order to achieve this, usually, 2 full 360 turns will do the job. Let rest 5-10 minutes. Do NOT play too much with the dough, you don’t want all the air to get out of it.
Put a light coating of flour on top of each boule. With a dough cutter or scraper, unstick the boule from the surface and flip it over. Shape your dough into 2 batards and place into bannetons dusted with either rice flour or all-purpose flour.
To make batard, once flipped. Gently fold the top to the middle, then do the same for the left side, right side. Then fold the bottom completely to the top. Make sure the seam is pinched. Note that the surface you will be looking at with the seam is the bottom. See this video to see it in action. Transfer in banneton, lightly flour, and let it rest for an hour. Cover loosely with plastic film and chill in the fridge overnight.