In a bowl, whisk together flour, graham cracker crumbs, baking powder and salt. In a separate large bowl, using an electric mixer on medium speed, beat the butter and sugar until light, about 2 minutes. Beat in the eggs until well combined. Reduce the mixer speed to low and slowly beat the flour mixture into the butter mixture. Divide the dough in half. Press half of the dough into the pan until the dough is even and flat. Spread with marshmallow topping and sprinkle chocolate chips on top. Scatter the remaining dough over the top in clumps. Don't worry about covering the top with the dough. The marshmallow and chocolate chips should peek through.