Grease a baking sheet or line it with parchment paper and lightly sprinkle it with flour.
Whisk together the starter, buttermilk, egg, and the melted butter.
In a separate bowl, mix together 2 cups of flour, the rolled oats (keeping a few aside to sprinkle on the top), baking soda, baking powder, and the sea salt.
Add the wet ingredients to the dry ingredients. Mix well. It will be a slightly sticky dough.
If it’s dry and crumbly add a little more buttermilk a Tbsp at a time. If it’s really sticky add some more flour a Tbsp at a time. It should be sticky, but dry enough to form it into a ball.
Form the dough into a ball and place it on the center of your prepared baking sheet.
Cut a deep “X” across the top.
Using a pastry brush, brush buttermilk on the top of the dough. Sprinkle oats on the top.
Bake for 35-40 minutes, or until the top is a beautiful golden brown.
Let the bread cool for 15 minutes before you cut it.
Notes
This sourdough soda bread is great with any meal just the way it is. But sometimes if we're having something Italian inspired, I'll brush it with garlic butter instead of buttermilk.