Irish Guinness Brown Bread - Miz En Place

Ingredients

• 1 cup quick-cooking oats (not instant) (plus extra for sprinkling)
• 2-1/4 cups whole wheat flour
• 1/4 cup all-purpose flour
• 1/2 cup dark brown sugar (lightly packed)
• 2-1/4 tsp baking soda
• 1 tsp baking powder
• 2 tsp kosher salt
• 1 (11- to 12-ounce) bottle Guinness extra stout beer (at room temperature)
• 1 cup buttermilk
• 5 tbsp unsalted butter (melted, plus extra for brushing the pan)
• 1 tsp pure vanilla extract
• Salted butter