Instructions

1. Place 4 ounces cream cheese in a large bowl and let sit at room temperature until softened, about 30 minutes. (Alternatively, microwave the cream cheese in a large microwave-safe bowl until just softened, 10 to 15 seconds.)
2. Coarsely chop 3/4 cup pecans or walnuts. Cook in a medium skillet over medium heat, stirring occasionally, until toasted and golden-brown, about 4 minutes. (Alternatively, bake on a rimmed baking sheet in a 400ºF oven until toasted and golden-brown, about 6 minutes.) Let cool completely, then coarsely chop.
3. If using, pick the leaves from 1 small bunch fresh tarragon until you have 1 1/2 tablespoons, then finely chop. Transfer 1 tablespoon to the bowl of cream cheese.
4. Add 1/2 cup sour cream, 1/4 cup packed light brown sugar, 1/4 teaspoon vanilla extract, and a pinch of salt and whisk to combine.
5. Pat 2 pounds red and green seedless grapes dry with paper towels or a clean kitchen towel and halve any grapes that are large. Add the grapes and 1/2 cup of the toasted nuts to the dressing. Gently stir until the dressing coats everything evenly. Transfer to a serving platter and top with remaining nuts and tarragon if using.