100g active sourdough starter, fed
500g (~4 cups) bread flour or all-purpose flour
350g room temp water
10g (~1 tbsp) kosher salt
The night before OR first thing in the morning, feed your sourdough starter and leave it on the countertop for at least 4 hours until almost doubled. You'll need 100g of starter total after feeding.
Once starter is at peak (almost doubled - bubbles visible on top), add starter, water, and the salt to your stand mixer bowl. Mix by hand with a spatula until the starter is completely dispersed into the water.
Add the flour and using the dough hook on the lowest speed, mix until there aren't any dry spots of flour clumps (~5-10min). It's okay if it's clumpy looking and not smooth. Remove dough hook, cover the bowl with plastic wrap, set aside to rest for 10-15 minutes.
Uncover the bowl and using a wet hand, grab one side of the dough and gently pull it (let it stretch without tearing), then fold it across the dough, rotate the bowl 90 degrees, and repeat 4 times until the bowl has been rotated a complete 360 degrees. Cover and let rest for an hour.
Repeat step 4 two more times until 3 rounds of stretch and folds have been performed (3 hours total). The dough should become smooth during this process and become airier. After the last round, cover and let it rise for ~2 hours until you see some larger bubbles on top and the edges slightly doming.
Prepare a bowl with crumpled parchment paper. Use a bit of rice flour if you have it and flour your clean counter (if you don't have rice flour, it's okay - it might be a little more wet and sticky causing it to be more difficult to shape but you can also use a spray bottle to mist your surface to help).
Gently turn out the dough onto the surface and shape using your favorite method (The Perfect Loaf has a great quick video showing how to shape a boule). Then, place the dough seam-side down into the bowl lined with parchment paper.
If making a same day loaf, cover with plastic wrap and set on counter to rise another 1-2 hours. Otherwise, cover with a light kitchen towel and place it in the fridge for an overnight rise to bake the next day.
Once ready to bake: Preheat your oven with the dutch oven inside to 450F (I do this without the lid to make it easy). If you're making a same day loaf, move your bowl of dough into the freezer or fridge during this preheating time ~20-25 minutes to flash chill it.
Once the oven is preheated, score your loaf ~1/4" deep across the middle. Add 2-3 ice cubes to the dutch oven to create steam. Quickly and carefully, grabbing by the parchment paper, lift the dough from the bowl and transfer it into the hot dutch oven. Cover with the lid. Bake covered for 25 minutes.
Optional: after the first 6 minutes of baking, carefully remove lid and re-score the same area again to help get a more prominent "ear". Re-cover and continue baking for the remaining 19 minutes.
Remove the cover and turn the oven temperature down to 425F. Bake uncovered for another 20-25 minutes until the outside is a golden brown all around.
Turn out the loaf from the dutch oven, remove the parchment paper, and let cool on a cooling rack for at least an hour before slicing. Enjoy!