In a large bowl, beat the heavy whipping cream and ¼ cup of the powdered sugar until stiff peaks form.
In a separate medium-size bowl, beat together the cream cheese and remaining powdered sugar until soft. Mix in the sour cream, cooled melted chocolate, and vanilla extract.
Blend and fold the whipped cream into the cream cheese mixture until combined. Spread evenly over the top of the crust.
Store cheesecake covered in the fridge for at least 5 hours to set. Cut into slices. Serve with fresh whipped cream and chocolate sauce, if desired.