• If you do not have a starter, then check out this complete guide on how to make your own sourdough starter from scratch.
• Your sourdough starter will need to be active and bubbly before combining the dough. Plan ahead and feed your starter until it rises (at least double) in your jar, then use when it is at its peak. If you want to make this bread using a starter from the fridge, then plan on having to feed him a few times (every 4-8 hours) before it is active enough to be used.
• Scheduling tip: I like to feed my starter early morning, then combine + stretch and fold the dough at around lunchtime. The dough will ferment all afternoon. Then, in the evening, I shape the dough into a boule, place in the proofing basket and transfer in the fridge for a cold final proof. The next morning, I score and bake. This is what works well for me, although you might prefer a different scheduling.
• Make sure to watch the video on how I make this bread. A visual explanation is very helpful when making sourdough!

Combine the dough

• In a large mixing bowl, add the sourdough starter and warm water. Stir until combined. Then add the bread flour, whole wheat flour and salt. Stir until mostly combined and no more dry spots of flour are visible. I like to start with a dough whisk, then use my hands. The dough will look shaggy and will be very sticky at this point, this is normal.
• Cover and let the dough rest for 20 minutes.

Stretches and folds

• Now, perform 3-4 series of stretches and folds with about 30 minutes of resting time in between.

  To stretch and fold: grab the dough on the opposite side of the bowl, pull it up until it cannot stretch anymore, then fold it back down on the dough. Rotate the bowl about 90º and repeat with the dough on the opposite side. Keep going until the dough is too tight to stretch (I usually do about 4 stretches per session). Cover, rest for 30 min and repeat.

Bulk fermentation

• Cover the dough well and let it rise and ferment in a cozy spot. Depending on the temperature of your kitchen, this can take 4-8 hours. For a quicker fermentation time, then move your dough into a warmer area in your house. The dough is done fermenting when puffy, looks lighter and wiggles when moving the bowl. It might also have doubled in size, although not necessarily.

Preshape

• When done fermenting, then transfer the dough over a lightly floured clean surface using a bowl scraper. Then, loosely shape the dough into a ball by pulling on the edges and bringing them in the middle of the dough (press them into the dough). It might look like a dumpling. Flip the ball to place the seam down on the counter. Cover and let it rest for 20 minutes.

Shape

• Flip the ball of dough back with its smooth surface on the counter and pull/stretch it to form a rectangular or square shape.
• Then fold the top part into the middle of the dough, then fold both sides as well on top of the dough. Then, grab the top part and roll it down until the seam is on the counter.
• Use both your hands to drag the dough on the counter by pushing the top part of the ball towards you. Then slightly rotate the ball and repeat. The top part of the dough should tighten up and be very smooth.

Final proof

• Sprinkle flour into your banneton or proofing basket and also some over the top of your ball of dough. Use a bench scraper to grab and lift the dough and flip it into the banneton so the seam side is up. Cover well and place in the fridge overnight (or for 12-36 hours, can also be done at room temperature for about 2 hours)

Score and Bake

• At least 30 minutes before you want to bake the bread (1 hour is better), place your Dutch oven in your oven and preheat to 450º.
• When the oven is really hot, then take your proofed dough out of the fridge and flip it over a piece of parchment paper (you can use a small board to ease the process). Score the dough as you wish and transfer it to the hot Dutch oven.
• Cover and bake for 30 minutes. Then, uncover and bake for 5-7 minutes or until the crust is golden brown.

Cool down

• Once done baking, take the bread out of the Dutch oven by pulling on the corners of the parchment paper. Let the bread completely cool down before slicing, or at least 2 hours (this is an important step!). Enjoy!