Preheat the oven to 425 degrees F (220 degrees C).
Combine Stone Ground Whole Wheat Flour (3 cup), All-Purpose Flour (1 cup), Baking Soda (1 teaspoon), and Salt (1 teaspoon).
Add Buttermilk (1 1/2 cup), up to 1 3/4 cups, enough to make a stiff dough.
Sprinkle a little flour on a baking sheet and place dough on it.
Shape into a round shape and use a sharp knife to slice a large X about an inch deep across the entire surface.
Bake for 30-40 minutes, until risen and golden-brown on top. The bottom should sound hollow when tapped.
Wrap in a clean towel and cool completely on a rack before slicing.