Irish Soda Bread

2 cups all-purpose flour
1 1/2 cups whole-wheat flour
1/2 cup oat flour **
1 teaspoon salt
1 teaspoon baking soda
1 1/2 to 2 cups buttermilk
1 egg, lightly beaten

Preheat oven to 425 degrees.
Combine flours, salt and baking soda in a large mixing bowl. Make a well in the center of the flour mixture and add the buttermilk all at once. Mix with a wooden spoon until dough is too stiff to stir. (Do not overmix.) Dust dough with additional flour and form into a round loaf. Resist the temptation to knead. (It is kind of wet so make sure to flour your hands well.) Place dough in a greased cast-iron skillet or on a baking sheet. Using a serrated knife, cut a cross into the top of the dough, about 1-inch deep. Brush top with beaten egg. Bake until the bread is golden brown and the bottom sounds hollow when tapped, about 35 to 40 minutes. Cover loosely with foil after 25 to 30 minutes to prevent overbrowning. Remove from oven and cool for 5 to 10 minutes on a wire rack. Serve warm with butter.

** To make oat flour, place rolled oats in a mini food processor and process them until very fine.