Preheat your oven to 400°F (200°C) and unfold the puff pastry on a clean surface. Cut into squares, brush with melted butter and sprinkle with salt. Bake for 12–14 minutes until golden and puffed.

Let the pastry cool on a wire rack for about 10 minutes to prevent the filling from becoming soggy.

In a mixing bowl, chop the cooled cooked chicken and add in chopped celery, halved grapes, finely diced onion, and mayonnaise. Season with salt and optional seasoning to taste.

Assemble the puffs by spooning 2-3 tablespoons of the chicken filling onto half of each pastry square. Cover with another square and seal. Repeat until all ingredients are used.

Arrange the assembled puffs on a platter and serve them fresh, warm, or at room temperature.