Mix flour and water until combined, then rest for 30 minutes.

Add starter and salt, mixing until a cohesive dough forms.

Perform stretch-and-folds every 30 minutes for 2 hours, adding cheese and jalapeños during the second fold.

Let dough bulk ferment at room temperature until slightly risen and airy.

Shape dough into a tight round or oval and place in a floured banneton.

Cold proof in the refrigerator for 8 to 12 hours.

Bake in a preheated Dutch oven at 475°F until golden and fully cooked.