Source: Eloise O'Brien (his wife)

4 cups whole-wheat flour
2 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 teaspoon sugar (optional)
About 1 1/4 cups buttermilk

Mix together all the dry ingredients; add enough buttermilk to form a soft dough. Turn out on lightly floured board; knead lightly. Form dough into a circle; place in greased 9-inch baking pan or on greased baking sheet. The dough should be about 1 1/2 to 2 inches high. Cut a cross 1/2 inch deep over the top with a floured knife. This helps bread cook more evenly.

Bake in preheated 400 degree F oven for 40 minutes, or until loaf sounds hollow when rapped lightly on the base with the knuckles. Remove bread from pan; cool on a wire cake rack. Bread should not be cut until it firms up. Toast it for breakfast or tea; spread lavishly with butter.