Preheat oven to 350 degrees F.

Line an 8x8-inch baking dish with foil; coat with cooking spray.

In a medium bowl, stir together graham cracker crumbs, sugar and melted butter until well combined; pat into bottom of baking dish.

Bake for 10-12 minutes or until golden brown.

In a medium bowl, using a mixer on medium speed, beat together cream cheese and marshmallow cream until fluffy - about 1 minute.

Beat in cocoa powder, vanilla and eggs until combined - about 1 minute.

Stir in melted chocolate until combined.

Pour filling over crust, and bake for 25-30 minutes or until set, and no longer wobbly. Remove from oven.

Preheat oven broiler.

Evenly top cheesecake with mini marshmallows.

Broil for a few seconds until marshmallows start to brown.

Cool on a wire rack (drizzle with additional melted chocolate, if desired).

Place in the refrigerator or freezer until well chilled - about an hour or two.

Lift out foil from dish and slice cheesecake into bars.