Preheat oven to 190 degrees celsius (fan-forced). Lightly grease a minimum 6-cup capacity pie or baking dish and set aside.
Heat the olive oil in a frying pan over medium/high heat. Cook the chicken for 5 minutes or until golden and cooked through. Set aside in a bowl.
Add the garlic, bacon, mushrooms and herbs to the frying pan and cook for 5 minutes or until the bacon is cooked and all of the liquid from the mushrooms has evaporated.
Add the chicken back into the frying pan. Sprinkle over the flour and mix to combine. Cook for 1 minute.
Add the dijon mustard and chicken stock liquid. Bring to a simmer for 5 minutes or until the sauce has slightly thickened.
Remove from the heat and stir through the cream. Season with salt and pepper.
Pour the mixture into the prepared baking dish.
Use a knife to cut the pastry sheets into long strips. Arrange them in a criss-cross pattern over the top of the mixture.
Brush the pastry with the whisked egg and sprinkle with sesame seeds.
Bake for 30 minutes or until the pastry is puffed and golden.