Preheat oven according the brownie mix directions. Prepare the brownie batter in a large mixing bowl according to the package directions. Stir in the pecans, white chocolate chips and mini marshmallows. Pour the batter into desired size pan, and bake according to the brownie mix directions. When the brownies come out of the oven, pour the caramel topping over them while they are still hot. Serve with ice cream, if desired.