Preheat Oven:
Preheat oven to 375°F (190°C). Grease and flour a 9x5-inch loaf pan.
Mix Dry Ingredients:
In a large bowl, whisk together whole wheat flour, all-purpose flour, baking soda, salt, and brown sugar or molasses until evenly combined.
Add Buttermilk:
Gradually pour in the buttermilk, stirring with a wooden spoon until a sticky dough forms. The dough will be dense and slightly wet.
Shape Dough:
Transfer dough to the prepared loaf pan. Smooth the top with a wet spatula or your hands. Score a shallow cross on the top with a knife to allow steam to escape.
Bake:
Bake for 45–50 minutes, or until the bread is golden brown and a toothpick inserted in the center comes out clean.
Cool:
Remove bread from pan and let cool on a wire rack for at least 20 minutes before slicing.