Mix dough: Place 2/3 cup cornmeal and corn grits (or polenta) in a medium bowl. Gradually stir in boiling water until well blended and lump-free. Let stand until barely warm. Thoroughly stir 2 cups bread flour, whole-wheat flour, 3 tablespoons millet (or sesame seeds), sugar, salt and yeast in a 4-quart (or larger) bowl. Thoroughly stir yogurt and oil into the cornmeal mixture. Stir 3/4 cup ice water into the cornmeal mixture until smoothly incorporated. Stir the cornmeal mixture into the flour mixture, scraping down the sides and mixing just until the ingredients are thoroughly blended; it may seem too dry initially, but it usually comes together with sufficient stirring. The dough should be moist and somewhat sticky, but fairly stiff. If the mixture is still too dry, stir in just enough additional ice water to facilitate mixing, but don't overmoisten. If the dough is too wet, stir in just enough flour to stiffen slightly. Lightly coat the top with oil. Cover the bowl with plastic wrap.

First rise: Let the dough rise at room temperature (about 70 degrees F ) for 12 to 18 hours; if convenient, stir once partway through the rise. For convenience (and improved flavor), you may refrigerate the dough for 3 to 12 hours before starting the first rise.

Second rise: Generously coat a 31/2- to 5-quart Dutch oven (or similar ovenproof pot) with oil. Coat the bottom and sides with 1 tablespoon each cornmeal and millet (or sesame seeds). Vigorously stir the dough to deflate it. If it's soft and very sticky, stir in just enough bread flour to yield a firm but moist dough (it should be fairly hard to stir). Transfer the dough to the pot. Lightly coat the dough with oil, then smooth the top using a well-oiled rubber spatula or your fingertips. Sprinkle with the remaining 1 tablespoon each cornmeal and millet (or sesame seeds) and pat down. Put the lid on the pot or tightly cover with foil.

Let rise at warm room temperature until the dough is double the deflated size, 1 1/2 to 2 1/2 hours. (For an accelerated rise, see Tip.)

15 minutes before baking: Position a rack in lower third of oven; preheat to 450 degrees F . Generously sprinkle or spritz the loaf with water.

Bake, cool, slice: Bake the loaf on the lower rack, covered, until lightly browned and crusty, 60 to 70 minutes. Uncover and continue baking until nicely browned and a skewer inserted in the center comes out with just a few crumbs on the tip (or until an instant-read thermometer registers 204-206 degrees ), 10 to 15 minutes longer. Cool in the pot on a wire rack for 10 to 15 minutes. Turn the loaf out on the rack and let cool to at least warm before serving. The loaf is good warm but slices best when cool.

Make Ahead Tip: Wrap airtight and keep at room temperature for up to 3 days or freeze for up to 2 months.

Notes: Milled from high-protein wheats, bread flour develops strong gluten, resulting in well-risen loaves. It helps give breads with a high percentage of whole grains better structure and a lighter texture. Find it near other flours in most supermarkets.

White whole-wheat, made from a special variety of white wheat, is light in color and flavor but has the same nutritional properties as regular whole-wheat flour. Available in large supermarkets and in natural-foods stores. Store in the freezer.

Tips: To prepare "ice water" for this recipe, add a heaping cup of ice cubes to cold water and stir for about 30 seconds before measuring out the water.

You can turn your microwave into a warm, moist environment to help accelerate the second rise of the bread dough. Begin by microwaving 1/2 cup water in a 1-cup glass measure just to boiling. Set the water in one corner of the microwave, place the pan of dough on the other side of the turned-off microwave and close the door. The dough will double in size in 45 minutes to 11/2 hours.