01 - Dissolve orange gelatin in boiling water, stirring until fully dissolved. Add cold water and mix thoroughly. Allow mixture to cool for 10 minutes.
02 - Gently fold drained mandarin oranges and crushed pineapple into cooled gelatin mixture.
03 - Transfer mixture to a 9x13-inch glass dish or decorative serving bowl. Refrigerate for minimum 2 hours until completely set.
04 - Combine sour cream, mini marshmallows, and whipped topping in separate bowl. Fold together until evenly incorporated.
05 - Spread creamy mixture evenly over set gelatin base. Return to refrigerator and chill for additional hour before serving.