For brown soda bread, use 3 cups whole wheat flour and 3/4 cup unbleached flour
Source: The Art of Simple Food
Preheat oven to 450F degrees.Measure dry ingredients (flour, salt and baking soda) together in a large bowl.
Make a well in the dry ingredients and pour in 1 1/2 cups of the buttermilk.Stir, adding more buttermilk if needed. The dough should be soft but not wet or sticky.
Turn the dough onto a floured surface and knead just enough to bring the dough together.You know the dough is kneaded enough when you make an impression on the dough, it bounds back.
Do not over knead or the bread will be dense.
Turn it over and pat into a round loaf, about 1 1/2″ high.
Place on baking sheet and cut a cross into the top of the loaf with a knife. Cut fairly deeply into the dough, cutting all the way to the edges; this helps the loaf to rise properly.Bake for 15 minutes, lower the temperature to 400F degrees, and bake for another 30 minutes, or until done.
You will know the bread is done when it sounded hollow when knock at the bottom.