In a large stock pot over medium heat, add the oil, carrots, celery, onion and garlic.
Stir everything together and allow to cook until tender, about 10 minutes.
Add the seasonings and stir again, cooking another minute.
Add the chicken and stir everything together then start to add your chicken stock slowly to the pot, cook for 20 minutes or until the mixture has reduced, but liquid still remains.
In a small saucepan over medium heat, add the butter and melt.
Quickly whisk in the flour and then continue to stir for 30 seconds.
Remove from the heat and add to the chicken mixture, stirring together and adding the peas.
Season if necessary.
Pour into a large bowl to cool so it doesn't begin cooking the puff pastry.
Heat the oven to 375 degrees and line 2 baking sheets with parchment paper.
Cut the puff pastry into circles or squares and fill the center with the chicken mixture.
Place another piece of dough on top and fold the edges over to seal closed.
Place on a parchment lined baking sheet.
Brush with egg white and bake for 30 minutes or until golden.
Serve over a lightly dressed salad.