Combine the yeast and half the cornmeal in a large mixing bowl. Add 1/2 cup of the water and beat until smooth. Allow to rise in a warm spot until doubled in bulk, 30 to 45 minutes.
Stir the mixture to deflate it, and add the remaining water, milk, oil, salt and the remaining cornmeal. Stir to combine. Add enough of the flour, 1 cup at a time, to make a soft but workable dough, usually about 5 cups.
Turn onto a well-floured surface and knead vigorously for 5 minutes, until the dough is smooth and elastic. Shape into a ball and place in a greased bowl, turning it so as to cover all sides lightly with grease. Cover with a clean cloth and allow to rise until double in bulk, about 1 hour.
Punch the dough down and knead on a well-floured surface for 5 minutes. Replace in the bowl, allow to double in bulk again, then knead for 5 more minutes. Divide the dough in two and form into round balls. Place on a greased baking sheet or in individual greased cake pans and allow to double in bulk again.
Place a shallow pan of water in the bottom of the oven and preheat to 500 degrees F. Place the loaves in the center of the oven and bake for 15 minutes.
Reduce the oven temperature to 400 degrees F and bake an additional 15 minutes. Once the loaves are browned and produce a hollow sound when thumped, remove to cooling racks.