In a large mixing bowl, combine the frozen mixed fruit, thawed whipped topping, sweetened condensed milk, and Greek yogurt or sour cream. Stir gently until the mixture is smooth and creamy, about 2-3 minutes.

If desired, gently fold in your choice of chopped nuts and mini marshmallows, maintaining the lovely chunks of fruit.

Pour the mixture into a freezer-safe dish or molds. Smooth the top and level it for a neat presentation.

Cover with plastic wrap or a lid and freeze for at least 4 hours, ideally overnight.

Before serving, remove from the freezer 10-15 minutes in advance to soften slightly for easier scooping.