This classic Jewish delicatessen rye bread doesn't actually have any corn in the dough, though plenty should be used on the baking sheet. It should be dense, but not dry, and the crust should be crisp and crunchy. Adapted from a recipe in _Better Than Store-Bought_ by Wittie and Colchie (1979). The starter will make about 2 cups, a bit more than needed for the bread. It can be fed like any sourdough starter, and stored in the refrigerator.