Preheat the oven to 350 and line (2) 9x9 cake pans with foil. Extend the foil over the sides.
Spray foil with non-stick cooking spray, then flour.
Mix butter, granulated sugar and brown sugar in a large mixing bowl and beat until fluffy.
1 1/2 cups unsalted butter, 1 cup granulated sugar, 1 1/2 cups light brown sugar
Add melted chocolate, vanilla and cream, mixing well.
3 oz unsweetened chocolate, 1/4 cup heavy cream, 2 tsp vanilla extract
Mix in eggs.
6 large eggs
In a separate bowl, combine flour, baking soda and cocoa.
2 1/4 cups all purpose flour, 1/2 cup unsweetened cocoa powder, 1/2 tsp baking soda
Slowly add the flour mixture to the wet ingredients.
Divide the batter, pouring half into each prepared pan Bake on the center rack of the oven for about 25 minutes. The cake is done when a toothpick inserted into the center comes out clean.
Remove cakes from the oven and sprinkle marshmallows over each one, then top each with a cup of pecans.
10 ounces mini marshmallows, 2 cups chopped pecans
Return the cakes to the oven and bake just until the marshmallows begin to melt.
Remove from oven and leaving cakes in the pans, cool on a cooling rack.