Preheat your oven to 400°F (200°C). Unfold thawed puff pastry on a floured surface, cut into squares, brush with melted butter, and sprinkle with salt. Bake for 12-14 minutes until golden.

Remove puffs from oven and cool on a wire rack for about 10 minutes.

Prepare the filling by chopping cooled chicken and mixing it with celery, grapes, onion, mayonnaise, salt, and seasoning.

Slice cooled pastry squares in half, fill with chicken mixture, and cap with the top half. Use toothpicks if needed.

Arrange puffs on a platter and serve warm or at room temperature.