Preheat oven to 400°F (200°C). Roll out chilled puff pastry and cut out 3-inch circles. Stack circles with parchment paper in between and chill for 15 minutes.

Place stacked circles on a lined baking sheet and bake for 15-18 minutes until golden brown. Cool on a wire rack.

Combine shredded chicken, Greek yogurt, diced grapes, chopped celery, salt, and pepper in a mixing bowl, mix until well-coated.

Cut a small circle out of the center of each cooled pastry cup to create a well. Fill each with chicken salad, mounding slightly over the edges.

Garnish with chopped chives just before serving. Enjoy while warm and crisp.