I struggled for ages to work out what to do for a gravy. Borlotti bean water is a simple but reasonable suggestion for a solution.
Liquid from a can of borlotti beans (drain them in a sieve for a few minutes)
Dice chicken and fry in a frying pan with rapeseed or sunflower oil.
Drain off fat and add diced mushrooms and sliced onion. Add sage and thyme whilst cooking.
Transfer to a warming saucepan and add the borlotti water.
Add salt and pepper to season and more sage and thyme if you like.
Transfer to mini casserole dish or foil tin.
Cover with foil and continue to heat in the oven for anything from 10 mins to 30 mins.
I usually serve in the crock dish to keep it warm for longer, tipping the remaining gravy over the veg towards the end of the meal!