Heat oil in medium frying pan, cook onion, celery and garlic, stirring, until onion softens.
Add chicken and cook until chicken just changes colour, add mushrooms and cook lightly.
Add flour, cook, stirring for 1 minute.
Remove from heat and gradually add cream. When combined, return pan to heat and cook, stirring, until mixture boils and thickens.
Stir in parsley; cool.
Preheat pie cooker and spray lightly with olive oil spray. Cut rounds of puff pastry for base and top; placing bases in pie maker. Spoon in filling, cover with top and press edges together using a fork or spoon to firmly seal. Sprinkle with sesame seeds. Close lid of pie maker and bake until browned all over. Remove from pie maker and allow to cool slightly before serving.
Recipe by Mrs Organised at http://www.mrsorganised.com.au/2015/04/05/chicken-mushroom-pies/