Place the blackberries on the bottom of the mug (It's better if you use a ramekin since it's flat and wide) .
In a small bowl add the toppping ingredients and mix until you have a dough (It will be really thick and sticky). With a spoon place the topping on the frozen berries.
Place the mixture in the microwave and cook for 2 1/2 minutes.
You can also put this in the oven at 350 degrees for 8 to 13 mintues.