In a large bowl, beat butter and molasses until blended. Add egg yolks and egg, 1 at a time, beating well after each addition. Beat in pumpkin and vanilla., In a small bowl, combine the flour, cinnamon, ginger, baking powder, baking soda, allspice and salt. Gradually add to the molasses mixture. Pour into a greased 13x9-in. baking pan. Sprinkle with marshmallows, pecans and chocolate chips. Bake at 350° for 20 minutes., Meanwhile, in a small bowl, beat egg whites on medium speed until soft peaks form. Gradually beat in brown sugar, 1 tablespoon at a time, on high until stiff glossy peaks form and sugar is dissolved., Remove gingerbread from oven; spread with meringue. Bake until meringue is lightly browned, 9-11 minutes longer. Cool completely. Cut into bars.