From http://inthekitchenwithkath.com
(Adapted from the recipe in Beard on Bread, by James Beard)
3 cups (456 g. of Bob's Red brand) whole wheat flour
1 cup (120 g. of King Arthur's Unbleached) all-purpose flour
1¼ teaspoons fine sea salt, or 1 teaspoon table salt
1 level teaspoon baking soda
2 teaspoons aluminum-free baking powder
1 ½ – 1¾ cups buttermilk
Preheat the oven to 375˚.
Combine the dry ingredients in a bowl and stir well with a fork.
Add 1½ cups buttermilk and stir well. You want a soft dough, like a biscuit dough. It it’s too dry, add an additional ¼ cup of buttermilk.
Knead the dough on a floured board for 2 or 3 minutes until it is a smooth ball. (A dough scraper can be very handy if the dough starts to stick. Just scrape it up and add a bit more flour to the board.)
Put the dough on a buttered baking sheet (or on a buttered piece of parchment paper on a baking sheet).
With a sharp knife, cut a cross in the top of the dough.
Back for 40 – 45 minutes until the bottom sounds “hollow” when tapped. You can also use an instant read thermometer—the bread should register about 190˚ in the center.
Let the bread cool on a rack before slicing.