Note: I could not get large vol-au-vent cases and used medium ones, they are just too small you can't fit enough filling in so there is too much pastry. For photo purposes I didn't overfill, but if this size is all you can get I suggest over stuffing and pouring extra filling and sauce over the top when dishing out. It doesn't look as pretty but you get a good ratio of filling to pastry and it still tastes delicious. The quantity of filling is for large cases and works well, but is to much for such small cases (hence over stuff). I used 2 cases for myself but gave 3 to my hubby.
Heat oil in a pan and add onion and garlic, cook until onion softens, add mushrooms and cook until soft. Set aside.
Wipe pan clean and add some more oil add seasoned breasts and cook both sides until cooked through. Remove and chop chicken into chunks. Set to one side.
Pour milk in a pan with stock and heat. Add a little water to cornflour mix and pour half of the liquid into the milk, stir until mixture thickens slightly.
Add wine, Dijon mustard, cayenne and cream stir to combine, add the rest of the cornflour and stir until mixture thickens.
Return mushrooms, onion and chicken to cream mixture, add the thyme and avocado and stir in gently to combine. Keep hot until serving.
Place vol-au-vent cases on an oven tray. Bake in a moderate oven about 5 Min's or until heated through.
To serve place cases on plate and spoon filling into them. I served mine with honeyed carrots and buttery garlic spinach.