In an over sized mug whisk together the dry ingredients.
Add the wet ingredients to the mug and mix until you have a smooth but thick batter.
Place the chocolate pieces on top of the batter, pressing lightly. Add 1 tablespoon of hot water on top.
Microwave at high heat for 1-2 minutes. The exact time will depend on your microwave.
The cake is done when the edges are slightly set but the middle is still a bit wet. Do not over cook.
Let the cake cool for about 10 minutes. The cake will sink slightly.
Serve with whipped cream and top with Hershey's chocolate syrup.