How to Make It
In a medium bowl, mix the yeast with 1/2 cup of warm water and 1 teaspoon of the molasses; let stand until foamy, about 5 minutes.
Melt the butter in a medium saucepan; pour out and reserve 2 tablespoons, leaving 3 tablespoons in the pan. Add the buttermilk to the pan and cook over low heat just until warm to the touch, about 2 minutes.
In the bowl of a standing electric mixer fitted with a paddle, combine the whole wheat flour, cornmeal, oats and salt. Add the buttermilk mixture and the remaining molasses; beat at low speed for 2 minutes. Add the yeast and the rice; beat for 1 minute. Beat in the potato flakes and 1 cup of the bread flour. Beat in 3 cups of the remaining bread flour, 1/2 cup at a time, until a soft, slightly sticky dough forms, about 5 minutes.
Cover the dough with plastic wrap and let rest for 10 minutes. Using a dough hook, knead the dough at low speed for 6 minutes. Scrape onto a lightly floured surface and knead until smooth and no longer sticky, adding up to 1/2 cup of the remaining bread flour.
Lightly oil a large bowl, add the dough and turn to coat; cover with plastic wrap. Let the dough stand in a warm, draft-free spot until doubled in bulk, 1 1/2 hours.
Brush two 8 1/2-by-4 1/2-inch loaf pans with some of the reserved melted butter and sprinkle lightly with the sesame seeds. Turn the dough out onto a lightly floured surface and cut in half. Shape into loaves and gently ease into the prepared pans. Alternatively, for braided loaves, quarter the dough and roll each piece into a 12-inch-long rope. Loosely twist 2 ropes together and ease the loaves into the pans, tucking the ends underneath. Brush the loaves with melted butter and cover loosely with plastic wrap; let stand until risen 1 inch above the rims of the pans, about 1 hour.
Preheat the oven to 375°. Bake the loaves in the center of the oven for 50 minutes, until risen and golden and an instant-read thermometer inserted in the centers registers 190°. Brush the tops with the remaining butter; then turn the loaves out onto wire racks to cool completely.