To make sweet sticky "sushi" rice: In a medium saucepan over medium-low heat, melt the butter and marshmallows until completely soft. Remove from the heat and stir in the cooked rice until well blended. Spray the nigiri mold or ice cube tray lightly with nonstick spray. Take slices of the fruit medley and place in the bottom of the mold or ice cube tray. Spoon in rice and press gently into the fruit. Unmold the "sushi" and top with mini chocolate chips and toasted coconut, if desired.