Preheat your oven to 425°F (220°C) and prepare a 9x5-inch loaf pan by greasing it or lining it with parchment paper.

In a mixing bowl, combine the whole wheat flour, all-purpose flour, baking soda, salt, oats, and brown sugar (or honey). Whisk until mixed.

Create a well in the dry mixture and pour in the buttermilk, adding honey if using. Stir gently until just combined.

Transfer the sticky dough into the prepared loaf pan and smooth the top. Optionally sprinkle rolled oats on top.

Bake for 30 minutes, then reduce the temperature to 400°F (200°C) and bake for an additional 15-20 minutes.

Remove from oven and let cool in the pan for about 10 minutes before transferring to a wire rack to cool completely.