Puree cottage cheese in a food processor until smooth. Transfer the pureed cottage cheese to a large bowl and whisk in the dry Jell-o mix until thoroughly incorporated. Use a rubber spatula to fold in the whipped topping until no streaks remain. Fold in mandarin oranges. Cover and refrigerate for at least 2 hours. If desired, serve topped with a dollop of whipped cream or whipped topping and fresh orange slices. For a little added flavor and texture, you can also fold in 2 cups of miniature marshmallows.