Dissolve sourdough starter in water, mixing to remove lumpiness as much as possible

Mix flours and salt in a medium sized bowl

Combine wet and dry ingredients mixing gently and just thoroughly enough to moisten all of the flour

Cover bowl with plastic wrap or a shower cap and leave in a warm, draft free spot for 12-18 hours until dough has doubled. It will be very moist.

Dump dough onto a floured board, using a dough scraper if you have one (it makes it so much easier).

Gently flatten dough out to a rectangle, then grab one end and gently pull out, then fold over about 1/3 of the dough, as though you were folding a letter in thirds.

Repeat with the other end and then repeat the process once more from the opposite side so that you have a ball shape.

Cover ball with plastic wrap (a little spray oil or flour helps the wrap not to stick), let rest for 15 minutes.

Place a tea towel into a medium sized bowl and sift flour over the surface very thoroughly (don't skimp or it will stick!)

Cover with plastic wrap and let sit to rise for another 1 hour.

Preheat your oven to 500° with a cast iron combo pot or cast iron dutch oven (and lid) inside it. This will take about 30 minutes and your dough should be ready by then. Your pan must be very hot and it needs a lid to keep the moisture in.

Remove pot (very carefully!) from oven and invert dough into pot, or bottom of combo cooker. Quickly cut a few 1/4" to 1/2" slices into the top of the bread with a razor blade or sharp serrated knife and place lid on pot.

Bake covered for 30 minutes, then carefully remove the pot lid, reduce the heat to 450° and bake an additional 15 minutes.

Let cool completely on a rack. Use a serrated knife to cut when ready.