How to make
Braise the onions in the butter until they soften and attain a golden crisp, add the diced chicken and braise for 6 min. Add the mushrooms and braise another 4-5 min. with them. Next, pour in the white wine. Let the sauce reduce for about 3 min. and remove from the stove.
Heat the oven to 300°F (150°C).
For the Bechamel, melt the butter in a pot and gradually add the flour while beating nonstop with a whisk. Pour in the milk and broth and stir on medium heat until it thickens. Now you can add half a cup of wine but it is not mandatory. Lower the stove's heat and stir until you get a consistency suitable for a Bechamel sauce.
Cut the tops off the vol au vent and heat them for 8-10 min. Combine the chicken with the Bechamel and continue heating on the stove for 2 min. on low heat.
Fill the vol au vent with the sauce and cover with the tops. Sprinkle with finely chopped parsley.
