Preheat oven to 400 degrees F
In a pan heat the butter over medium heat, cook onions until softened.
Stir in the flour, salt, pepper and herbs. It will create a thick paste, let cook for 30 seconds once combined.
Slowly add in your milk and chicken broth and simmer until thick (this should only take about a minute).
Remove from the heat and add in your vegetables and chicken, mix well and add to a deep casserole dish. Set aside.
In a medium bowl combine the ingredients for the crust, mix until there are no lumps. It should be slightly thicker than a pancake batter. If you need to, add more bisquick (a little bit at a time).
Pour the crust mixture over the chicken mixture and place in the oven on the center rack.
Cook for about 30 minutes or until the crust is a nice golden brown!