1. Preheat the oven at 350F.
2. In a bowl add 1 cup butter, sugar and brown sugar and whisk well until it forms into a smooth mixture.
3. Crack an egg into the mixture, add vanilla extract and whisk with an electric whisk.
4. In another bowl mix all purpose flour, cocoa powder, baking powder and a pinch of salt.
5. Mix the dry mixture with the wet mixture.
6. Add buttermilk and whisk well with the electric mixture.
7. Bake the mixture in the preheated oven for about 15-20 minutes.
8. Remove from the oven and let it cool on a cooling rack.
9. Top with some whipped cream and sprinkle on it.