Yield: 9x5-inch loaf
Whisk together yeast, sugar, warmed milk, and stout beer in the bowl of a stand mixer. Allow to sit for 5-7 minutes to activate yeast.
Attach dough hook to stand mixer. Add bread flour, cocoa powder, espresso powder, and salt to mixer. Mix on low speed until dough starts to come together. Increase speed to medium and add coconut oil. Continue to mix on medium speed for 3-5 minutes until dough no longer sticks to the sides of mixing bowl.
Transfer dough to a large greased bowl. Cover and allow dough to rest for one hour at room temperature.
Punch dough down to remove any air bubbles. Pat the dough into a rectangle about 9 x 12 inches. Fold into into thirds like a business letter. Tuck in the sides. Place inside a well greased 9 x 5-inch bread loaf pan. Cover with plastic wrap and allow dough to rest for 20-30 minutes until bread rises to the top of the pan.
Preheat oven to 375 degrees F. Brush top of dough with egg wash. Top with rolled oats. Bake for 40-45 minutes until an instant-read thermometer inserted in center of bread loaf reads at least 200 degrees F. Rotate bread loaf midway through baking to ensure even cooking.
Allow bread to cool in pan for 5 minutes before unmolding. Allow bread loaf to cool to room temperature of a wire rack. Once bread has cooled, slice bread using a serrated knife.
Whisk together egg, salt, and water until smooth.