Irish Walnut Oatmeal Soda Bread

INGREDIENTS

2 1/2 cups

old-fashioned rolled oats, divided

1 3/4 cups

buttermilk

2 cups

all-purpose flour, plus more for shaping

1/2 cup

cake flour

1/2 cup

whole-wheat flour

1/4 cup

brown sugar

1 1/2 tsp

baking soda

1 1/2 tsp

cream of tartar

1 1/2 tsp

salt

2 tbsp

unsalted butter, at room temperature

1 cup

chopped walnuts, toasted

1 tbsp

melted butter, for brushing