Step 1
Place a rack within the heart of the oven and preheat to 350° F. Calmly grease an 8-by-4-inch loaf pan with butter and line with parchment.
Step 2
In a big bowl, stir collectively the entire wheat and all-purpose flours, oats, baking soda, and salt. Add the butter and, utilizing a pastry blender or your palms, reduce the butter into the flour till the combination resembles small crumbs and holds collectively barely when squeezed within the palm of your hand. Add the milk, treacle, and Guinness, then use a silicone spatula or wood spoon to fold the liquids into the dry elements simply till mixed. (Don’t overmix.) Switch the batter to the ready loaf pan, smoothing the floor with the spatula or the again of the spoon. Sprinkle with a beneficiant pinch of oats.
Step 3
Bake till a skewer inserted within the heart comes out clear, 45–50 minutes. Permit to chill barely, then unmold the loaf and slice to serve heat (or cool to room temperature earlier than slicing).
