Preheat the oven to 350 degrees.
Prepare the cupcake tin with liners.
In a mixing bowl combine the flour, sugar, cocoa powder, salt, and baking soda. Using a whisk, mix all the ingredients well. These are your dry ingredients.
In a separate mixing bowl whisk the egg, milk, vegetable oil, and vanilla together. These are your wet ingredients.
Combine the wet and dry ingredients together. This is your batter.
Add the boiling/hot water to your batter, mix well, and let stand for 1- 2 minutes. Your batter will be thin.
Pour the batter into the tins and bake for 15 - 20 minutes. While the cupcakes are baking you can begin making the frosting.
Remove and allow cupcakes to fully cool before adding frosting.