Preheat oven to 350 degrees F. Grease a 9in loaf pan and set aside.
Whisk together the dry ingredients in a large mixing bowl and set aside.
Pour Guiness into a large mixing bowl. Add sugar and whisk until the sugar has completely dissolved. Add the rest of the wet ingredients. Use a wooden spoon to ensure the ingredients are thoroughly mixed together. The mixture may curdle a bit because of the egg and melted butter, this is normal. Add the raisins and let them sit in the liquid for a minute or two to plump up.
Gently fold the dry ingredients into the wet ingredients, working in batches. Use your spatula to "cut" the flour into the batter, but be very careful not to over work the batter. The resulting batter should be runny and when you lift your spoon, the batter should fall like a ribbon (in terms of consistency, the batter should be a little thinner than pancake batter and a little thicker than cake batter). If the batter is too wet, add a 1tbsp more flour, if it is too dry, add more stout or water.
Pour the batter into the greased loaf pan, the batter should fill 2/3rd of the pan. If you have excess batter, make muffins! Bake for 1 hour and 30 minutes, or until a knife inserted into the middle of the bun comes out clean.
Make the glaze. Heat water and honey on the stove until the honey dissolves. Using a pastry brush, brush the honey and water mixture over the bread while it is still hot.
Let the bun rest for 20-30 minutes before slicing with a bread knife. For a firmer bun, place the loaf in the fridge to chill. Serve alone or with cheddar cheese and enjoy!