In the bowl of an electric mixer, whisk together the yeast and the warm water. Let stand about 10 minutes, until foamy.

Fit the mixer with the dough hook attachment, and beat in the cornmeal, molasses, butter, and salt. Mix in the flour, 1 cup at a time, to make a moderately stiff dough.

Turn the dough out onto a lightly-floured surface, and knead for 6 to 8 minutes, until smooth and elastic, adding only enough flour to prevent sticking.

Transfer the dough to a large bowl coated with vegetable oil, and turn the dough to coat all surfaces. Cover with a slightly damp towel and let rise in a warm, draft-free place for 1 to 1 ½ hours, until doubled in size.

Punch the dough down. Turn out onto a lightly-floured work surface, and divide it in half. Cover, and let rest for 10 minutes.

Preheat the oven to 375°F. Grease a large baking pan with butter, and sprinkle with cornmeal.

Shape each half of the dough into a ball. Place the balls, smooth sides up, on the prepared baking pan. Flatten each ball into a 6-inch round loaf. Cover and let rise for 30 to 45 minutes, until almost doubled in size.

Bake for 25 to 30 minutes, or until almost doubled in size.

Remove the bread from the baking pans. Serve warm, or cooled and toasted.