Preheat the oven to 350℉ & grease your standard loaf pan *see notes for recipe size & extra batter
Combine the flax meal with the first measure (½ cup) hot water whisk smooth then set aside for 5 minutes to thicken while you gather the rest of your ingredients
Into a large mixing bowl sift together both cocoa powders with the light brown sugar, add the second measure of hot water (1½ cups) along with the oil & extract whisk smooth
Add the flax paste & whisk smooth
Add the sifted flour with the baking powder, soda & salt & whisk to a smooth batter
Pour into the prepared loaf pan ¾ of the way to the top then bake 4 cupcakes with the excess batter. Alternatively you can use a large loaf pan to utilize all the batter
bake for approximately 45 minutes or when a toothpick inserted comes out with moist crumbs no raw batter
Cool in the pan until you can safely touch it without burning yourself then flip the loaf out onto a cooling rack & cool to cold
Meanwhile prepare the buttercream icing according to the instructions on that post