Line an 8x8 pan with nonstick foil.
In a medium saucepan over medium low heat, stir the chip, butter and condensed milk until all melted.
Remove from the heat and cool about 3 minutes.
Gently fold in the marshmallows and Graham cracker pieces.
Swirl in the marshmallow cream leaving it streaky in appearance.
Spread in pan and chill 4 hours.
Slice.