Preheat the oven to 450F/230C. Line a baking tray with parchment paper and set aside.
In a large bowl, combine the flours, oats, salt and baking soda. Mix throughly.
Make a well in the middle of the flour and pour in the buttermilk and molasses.
Using a fork, stir the liquid, gradually bringing the flour in from around the edge.
With floured hands lightly knead to a soft dough.
Shape the dough into a round and place it on the parchment paper. Press the dough flat about 2 inches/5cm thick. Use a sharp knife with a long blade to cut a deep cross on the top.
Bake in the oven for 15 minutes, then reduce the oven temperature to 400F/200C.
Continue baking the bread for another 20-25 minutes or until the base of the bread sounds hollow when tapped.
Transfer to a wire rack and allow it to cool slightly. Serve warm.
Video
Notes
Storage: Keep your soda bread fresh by letting it cool completely, then wrapping tightly in plastic or foil. Store at room temperature for 3-4 days, in the fridge for up to a week for longer freshness, or freeze for up to 3 months. To refresh stale bread, warm it in a 300°F oven for 5-10 minutes.