Grease two 4-cup molds, such as pudding molds, small heatproof bowls, or 28-ounce cans. Have ready a pot or Dutch oven large enough to hold both molds. Place a rack, trivet, or folded towel in the pot. Bring a separate large pot of water to a boil while you prepare the batter.

Whisk together thoroughly in a large bowl:

Whisk together in another bowl:

Add the buttermilk mixture to the flour mixture and stir until well blended. Divide the batter between the molds. If the pudding molds have lids and clips, grease the inside of the lids and secure the clips. Otherwise, cover the molds with a double thickness of greased foil, greased side down, and secure tightly with kitchen string.

Set the molds in the prepared pot. Pour boiling water into the pot until it reaches halfway up the sides of the molds. Cover the pot and set it over high heat. When the water comes back to a boil, adjust the heat so that the water simmers gently. Steam until a toothpick inserted in the center comes out clean and the breads pull away from the sides of the molds, about 1 hour, replenishing the water in the steamer as necessary.

Transfer the molds to a rack, uncover the breads, and let cool for about 20 minutes before unmolding. If the breads were steamed in cans and they prove difficult to unmold, remove the bottom of the can with a can opener and push the breads out. Serve warm, or let cool completely on the rack before wrapping to store. To slice without crumbling, use a tough string or unflavored dental floss and a sawing motion.