Prepare the Grapes. Start by washing and drying the grapes thoroughly. Remove the stems and cut them in half if you prefer smaller pieces. Place them in a large mixing bowl.
Make the Creamy Dressing. In a separate bowl, beat together the softened cream cheese and Greek yogurt until smooth and well combined. Add granulated sugar and vanilla extract to the mixture, and continue to mix until the dressing is fluffy and well-blended.
Combine the Grapes and Dressing. Pour the creamy dressing over the grapes. Gently fold the mixture together using a spatula or spoon until the grapes are well coated with the dressing.
Prepare the Topping. In a small bowl, combine the chopped nuts (pecans or walnuts), melted butter, and brown sugar. Stir until the nuts are coated with the sugar. This will give them a nice caramelized crunch.
Optional: If you like the extra sweetness and texture, fold in mini marshmallows for a chewy element.
Assemble the Salad. Spoon the dressed grapes into a serving dish or individual bowls. Top with the brown sugar-coated nuts and marshmallows. You can garnish with a light dusting of cinnamon for an added flavor boost.
Chill and Serve. Refrigerate the salad for at least 1 hour before serving to allow the flavors to meld and the salad to chill. It’s best served cold, but if you're in a hurry, you can serve it right away!