1. Initial Mix (Fermentolyse)
In a large bowl, mix 4 cups of flour, ½ cup sourdough starter, and 1½ cups water until you have a shaggy dough. Try not to have any dry flour sitting on the bottom. Cover the dough—I prefer a glass Pyrex bowl with a plastic lid so it doesn't dry out. Let it sit for 30 minutes. This allows the water and starter to penetrate the flour and make the dough workable.
Note: If you don't have a bowl with a lid, you can use cling wrap or some people use a wet towel. if you use wet towels rewet them frequently so the dough doesn't dry out.
2. Add Salt
Dissolve 2 teaspoons of salt in about 1/8 cup of lukewarm water, which helps the grains dissolve much faster. Pour this salt mixture over your dough and knead it by hand until the water is fully incorporated.
3. How to "Stretch and Fold":
Reach underneath the dough and grab one side. Gently stretch it out as far as you can without tearing, then fold it back into the middle. Repeat this all the way around the dough 3 times. This is one "set."
Do 3-4 sets of stretch and folds, letting the dough rest covered for 30 minutes between each set. This develops the gluten strength and that signature chewy texture. If the dough feels pretty elastic after 3 sets, you're good; if not, do a fourth.
4. Bulk Rise (Timing & Temperature)
After your folds are done, let the dough rest. Sourdough is very affected by temperature; in the hot summer it may be ready after your last set of stretch and folds, but in winter it may need 4 extra hours. Look for these signs: the dough should be airy, stretchy, hold its shape, while having several air bubbles. If you aren't ready to bake when the dough is, put it in the fridge covered with a lid or plastic wrap to shape later.
5. Preheat, Final Shape, and Fillings
Preheat your Dutch oven to 450°F (or standard oven to 375°F).
On a lightly floured surface, shape the dough into a square or rectangle just under 1/2 inch thick. Sprinkle on ½ to 1 cup of shredded cheese (Sharp Cheddar or Colby-Jack) and spread sliced jalapeños evenly over the top. Adding them at the end prevents the fillings from tearing the dough.
6. Rolling and Tension
Roll up the dough, tucking the end into itself. Then roll it the other direction to turn it from a long shape into a ball. Take the sides and tuck them underneath to make it as round as possible, keeping all seams on the bottom.
7. Scoring and Baking
Place the dough on a parchment paper "sling." Cut a slash 1/4 to 1/2 inch deep on top to allow for expansion. I don't recommend doing fancy patterned scoring because the fillings make it easy to tear and hard to do minute scoring.