Combine flour and the next 6 ingredients in a large bowl, stirring with a whisk.
Combine sour cream, butter and egg well. Add egg mixture to flour mixture. Stir to form a soft dough. Turn dough out onto a lightly floured surface. Knead 7 or 8 times.
Divide dough in half. Place 1 dough portion on each of 2 baking sheets lightly greased with butter and sprinkled with 1 ½ tablespoons cornmeal. Turn to coat top of dough. Roll each portion into a 12 x 8-inch rectangle about 1/8 inch thick.
Bake for 15 minutes or until browned and crisp. Remove from pan and cool completely on wire rack. Break each sheet into 12 crackers.