Step 1
Place the sourdough starter water olive oil salt sugar yeast and flour in that order into the pan of a bread machine set the machine on the dough cycle and start the machine.
Step 2
After the machine has finished its cycle turn the dough out onto a floured surface and knead several times; mix in more flour if the dough is very sticky. Cut the dough in half and roll each piece of dough out into a rectangle about 8 by 12 inches and 1/2-inch thick. Roll the rectangles into loaves the long way pinch the seams and taper and pinch the ends of the loaves.
Step 3
Line 2 baking sheets with parchment paper and sprinkle paper with cornmeal. Place the loaves gently onto the prepared baking sheets cover loosely with plastic wrap and let rise in a warm place until doubled about 30 minutes.
Step 4
Place a large baking stone onto the center rack of oven and place a baking dish onto a lower rack. Preheat oven to 375 degrees F (190 degrees C). Carefully pour boiling water into the baking dish.
Step 5
Remove plastic wrap from loaves and slash several 1/2-inch deep cuts into each loaf with a sharp knife. Whisk egg yolk and milk together in a small bowl until thoroughly mixed and brush the loaves with the egg yolk mixture.
Step 6
Place the loaves into the preheated oven on top of the baking stone and quickly spray the inside of the oven 4 or 5 times with a water-filled spray bottle. Shut oven door; wait 1 minute and spray again; repeat twice more spraying the oven 4 times with water at 1-minute intervals.
Step 7
Bake about 15 minutes and remove the water-filled baking dish. Continue to bake until the bread is browned and the loaves make a hollow sound when thumped about 15 more minutes. Remove bread to cool on racks.