Prepare chicken: Chop the chicken into similar size chunks and season all over with salt and pepper.
Prepare mushrooms: Wipe the mushrooms then either slice thinly or chop them roughly. If using button mushrooms use them whole.At this point preheat the oven to 375 F/190 C/gas mark 5.
Brown chicken: Heat 1 tablespoon of oil, add the chicken and cook over a fairly high heat for about 2 minutes on each side (it should still be raw inside). Transfer to your casserole dish (along with the juices).TIP: Brown the chicken in 2 batches to avoid overcrowding the pan.
Fryonion: Using the same pan heat the remaining oil, add the onion and fry over a gentle heat for 4-5 minutes until softened, stirring often. Pour in the wine, increase the heat and cook for another minute or so.
Add mushrooms: Add the chopped mushrooms, cover and cook over a medium heat for about 5-6 minutes until the mushrooms start releasing water, stirring occasionally. Remove the lid, increase the heat and continue cooking until almost all the water has been absorbed and the mushrooms are lightly browned, stirring frequently. Towards the end of cooking add the crushed garlic.
Thicken: Add the flour and stir until no longer visible.
Add stock: Pour in the stock (once cooled), add the thyme and cook for a minute or so until the sauce has thickened. Remove from the heat and stir in the cream cheese. Taste the mixture and adjust the seasoning as needed.
Assemble casserole: Pour the mushroom sauce over the chicken. Scatter over 3 tablespoons of grated gruyere cheese.
Bake: Place in the centre of the oven and bake for 20 minutes or until the chicken is fully cooked. Remove from the oven and serve.
Notes
Brown the chicken in 2 batches to avoid overcrowding the pan. The chicken should be lightly browned but still raw inside (I used a similar method in chicken tomato pasta bake).
Adjust the amount of herbs and seasoning to your taste.
Cooking times may vary depending on the size of your chicken pieces.
Best served immediately. Leftover baked chicken mushroom casserole can be refrigerated for up to 3 days. The sauce will thicken after a while so you may need to add a drop of water to loosen it when reheating the dish.