Preheat oven to 350 F.
In medium bowl, sift together, cocoa, baking powder and salt.
Whisk in whole wheat flour.
In a small bowl, dissolve expresso powder in milk.
In another large bowl, mix together butter, sugar until light and fluffy.
Add milk mixture, egg and vanilla extract. Beat well.
Gradually add in flour mixture and mix until just combined.
:- Do not mix too much.
Pour batter into an 8 inch square baking pan which is greased.
Bake 25 - 30 mins or until a toothpick inserted comes out clean.
Cool for 10 mins and remove to wire rack to cool.
:- A chocolate icing can be added on top, tastes even better! :)