Heat oven to 350. Grease & flour 13 x 9 inch pan. Lightly spoon flour into measuring cup, level off. In a medium bowl, combine flour , graham crumbs, baking powder, baking soda, & salt; mix well.
In a large bowl, beat brown sugar, shortening & eggs until well blended. Add flour mixture & milk; mix at lo speed until well blended. Stir in 2/3 c. chocolate chips. spread batter into greased and floured pan. Bake at 350 for 25 - 35 min. or until done. Cool 15 min.
Meanwhile in a small suacepan melt remaining 1/3 c chocolate chips over low heat. Spoon t. of marshmallow creme onto warm cake; carefully spread with knife dipped in hot water. Drizzle with melted chocolate, swirl chocolate through marshmallow creme to marble. Cool completely.