Preheat oven to 350°F Grease a 9×13-inch baking pan.
In a medium saucepan, melt the chocolate, butter, and 3/4 cup of the semisweet chocolate chips on medium heat. Stir occasionally while melting. Set aside and cool for 5 minutes. In a medium bowl, sift the flour, baking powder, and salt. Set aside. In a large bowl, place the eggs and whisk thoroughly. Add in the sugar and vanilla. Stir the melted ingredients into the egg mixture, mixing well. Stir in the dry sifted ingredients and mix well. Fold in the remaining 1/2 cup semisweet chocolate chips.
Pour the batter into the prepared pan, and even with a spatula. Bake for 25 to 30 minutes, or until a cake tester inserted into the corner of the pan comes out with moist crumbs.
Remove the brownies from the oven, and immediately sprinkle the marshmallows over them. Return the pan to the oven for 3 more minutes.
While the brownies are baking, place the chocolate chips, peanut butter, and butter in a medium saucepan. Cook over low heat, stirring constantly until melted. Remove from heat, add the cereal,and mix well. Allow this to cool for 3 minutes or so.
Spread the mixture evenly over the marshmallow layer. Refrigerate until chilled before cutting. Makes 12 3×3-inch bars.