In a small microwavable bowl, microwave chocolate chips and condensed milk on high for 1 to 2 minutes, stirring occasionally (stopping about every 30 seconds to stir), until chips are melted. Stir to mix well. Pour into a 9-inch pie pan, spreading evenly.
Drop marshmallow cream by tablespoonfuls randomly over chocolate mixture. Microwave on high for about 30 seconds or until marshmallow cream is softened. Immediately with a knife, make several small swirls through marshmallow and chocolate, creating a marbled appearance.
Serve immediately with graham crackers for dipping.