Preheat your oven to 450 degrees
Evenly spread 1 tablespoon of softened butter throughout the interior of a 9"x5" bread pan and set aside
Combine 2 1/4 cups of whole wheat flour with 1 cup of old fashion oats, 1/4 cup of all-purpose flour, 1/2 cup of dark brown sugar, 2 1/4 teaspoons of baking soda, 1 teaspoon of baking powder and 2 teaspoons of salt in a large bowl and set aside
Whisk 1 cup of whole fat buttermilk with 5 tablespoons of melted butter, 1 teaspoon of vanilla extract and 1 bottle Guinness extra stout beer in a separate bowl until fully combined
Add the beer and buttermilk mixture to the dry ingredients and mix until everything is fully incorporated
Transfer the bread dough into the buttered bread panĀ
Sprinkle a few oats over the top of the bread dough
Place the bread pan onto a center rack in a preheated 450 degree oven and as soon as you shut the oven door, reduce the oven temperature to 400 degrees
Bake for 45 minutes
The bread is done with a toothpick comes out of the center dry and clean
Transfer the baked bread out of the bread pan and directly onto a cooling rack
Allow the bread to cool to room temperature before slicing
Store leftovers in an airtight container at room temperature