In a large mixing bowl, combine the whole wheat flour, sugar, soda and salt. In a separate bowl beat eggs until frothy and add buttermilk.
Combine milk mixture and softened butter with the flour mixture and beat with an electric mixer for 2 minutes. Add white flour gradually and turn dough out onto a floured board. Knead thoroughly. Divide dough in half and shape into 2 round balls. Flatten the tops slightly and, with a knife, cut an "X" about 1/2 inch deep. Put loaves on a greased cookie sheet or into 2 9x5-inch loaf pans. (For loaf pans, cut slash down center lengthwise.) Bake at 400 F for 50 minutes. Cool before cutting into thin slices.
Yield: 6 servings