Preheat the oven to 350. Line a 9 x 9 baking dish with foil or parchment, and set aside.
In a large bowl or the bowl of a stand mixer, mix together the butter, sugar, eggs, and vanilla. In a small bowl, whisk together the flour, cocoa powder, baking powder, and salt. Add the dry ingredients to the wet ingredients, and stir until just combined.
Pour the brownie mixture into the prepared pan, and spread evenly. Bake 20-25 minutes, or until a toothpick inserted one inch from the side of the pan comes out clean. Remove from oven and let cool completely.
In a microwave safe bowl, combine the semi-sweet chocolate chips and half and half. Heat on 50% power for 30 seconds, stir, and repeat, until the chocolate is melted. Stir in the marshmallow cream and spread the mixture over the brownies. Refrigerate until chilled.
Pour the caramel sauce over the top of the brownies and spread evenly. In a small microwave safe bowl, melt the milk chocolate chips at 50% power, stirring every thirty seconds. Drizzle the chocolate over the caramel layer, and serve.