Mix chicken with marinade in a bowl, cover and refrigerate for 2hrs. Cook in the air fryer at 185°C for 11 minutes, then turn over and cook for a further 11 minutes or until golden brown and cooked through but still juicy. Refrigerate until room temperature or cold.
Preheat oven to 190°C. Slice chicken and set aside. In a small bowl, mix egg wash ingredients and set aside.
Onto half the pastry squares, layer one slice of tasty cheese onto the center. Continue layering with onion and chicken, taking care not to spill outside the cheese shape – leaving a pastry boarder. Top with a dollop of cream cheese, then mozzarella cheese. Brush exposed pastry edges with egg wash.
Using a small sharp knife, carefully score three 2cm slits into the center of the remaining pastry squares. This will allow the pastry to expand.
Top the filled pastry squares with the scored pastry and gently press together along the border with a fork. Repeat for each parcel, then brush the top of each parcel with egg wash. Sprinkle with black sesame seeds and bake for 10 minutes, then turn and bake for a further ten minutes or until golden brown and flakey.
Serve while hot as a snack or entrée. Garnish with chopped chives.