Spray a large saucepan with nonstick spray.
Add onions and garlic.
Cook over medium heat until tender, about 5 minutes.
Add broth, potatoes, carrots, and beans.
Bring to a boil.
Reduce heat to medium-low.
Partially cover and simmer for 12 minutes.
The potatoes should be slightly undercooked.
Remove from heat.
In a small bowl, stir together mushroom soup and flour.
Add to vegetables, along with chicken, parsley, basil, thyme, and pepper.
Stir well.
Pour into a medium casserole dish.
To prepare crust, combine flour, baking powder, sage, and salt in a large bowl.
using a pastry blender, cut in butter or margarine until mixture resembles coarse crumbs.
Stir in milk.
Form a ball with the dough.
Add a bit more flour if dough is too sticky.
Roll out on a floured surface to fit top of casserole.
Place dough over chicken mixture.
Prick several times with a fork.
Bake at 400 degrees F for 25 minutes, until crust is golden brown.
Let cool for 5 minutes before serving.