Place all flour and water in a mixer bowl and mix on low speed until fully incorporated and you can’t see dry patches if flour. At this stage you don’t want to knead or develop gluten. It’s called autolyze and it helps flour absorb water better before th
Add salt and mix on medium speed until the dough clears the bowl. Add porridge amd starter and mix on low speed until it’s fully incorporated. Transfer the dough into an oiled plastic container and start BP(bulk proof).
It’s a very important stage of sourdough making process where we’re developing the dough structure through a series of folds and breaks between them. We want to make sure the dough is nicely fermented and strong before we move onto shaping.
Perform 4 S&F(stretch and folds) every 30 min and 2 S&F every 1h, then rest the dough for 1 extra hour. The total of bulk fermentation here is 5h( 4x30min+2x1h+1h=5h). If you’re not familiar with stretch and fold technique please look it up on YouTube.
After that divide the dough into 3 same size chunks( use scales to work out the exact weight if you want).
Round it up so you have a smooth dough ball and let rest covered for 30 min.
Shape into batards using technique that you’re most comfortable with and place into 1kg oval bannetones sprinkled with rice flour. Cover and place in the fridge at 5C for 18-24h.
Bake in preheated(250C for 1h) cast iron or clay pot at 250C covered for 15 min then 220C uncovered for additional 15min. Allow to cool for 1h before slicing. Enjoy;)