Irish Soda Bread

In a large bowl, mix the flours, baking soda and salt. Using your fingertips, rub in the cold butter or margarine until the mixture resembles coarse meal. Pour in most of the buttermilk; you may need slightly less, depending on the balance of white and whole wheat flour. Mix well, turn out onto a floured board and knead until smooth, about 5 minutes. Shape the dough into a round loaf. Cut a cross in the top with a sharp knife and put the loaf in a greased round pan, such as a cake pan or pie plate. Bake at 400 degrees for about 40 minutes. Let cool before cutting. Makes one 6 inch loaf.