Preheat oven to 350*F.

Grease the bottom and sides of an 8" round cake pan; line the bottom with waxed paper, grease the paper, and dust with graham cracker crumbs.

In a large heavy saucepan over medium heat, begin to melt the butter.

When it's half melted, add the chocolate and stir until the chocolate is half melted.

Remove pan from heat and stir until both are fully melted.

Stir in the sugar, eggs, vanilla, graham cracker crumbs, and marshmallows.

Pour and scrape the batter into the prepared pan and bake for 30 minutes, or until the top is browned, the edges are crusty, and the center is still soft.

Cool in pan on a wire rack for 20 minutes.

Run a knife around the rim of the cake, cover with waxed paper, and invert onto a serving plate.

Remove the pan and peel off the lining paper.

Cover with another plate and invert again; remove the top sheet of waxed paper and cool about 15 minutes more.

Serve with whipped cream, ice cream and fudge sauce, or dust with powdered sugar.