Using a double boiler method or your microwave, melt the chocolate until completely smooth.
Combine the melted chocolate, pureed pumpkin and arrowroot powder in a food processor until a smooth mixture is formed.
Transfer to a cake pan of your choice, and set in the fridge for at least 3 1/2 hours before slicing. Enjoy immediately with a dusting of cocoa powder and berries on top. Store in a sealed container in the fridge for up to 4 days.