I made this for three people, with three thighs and three drumsticks. My oval Le Creuset just accommodated them in one layer. For the quantity below, you probably need a 28cm saute pan, with a lid.
4 chicken thighs
1dstsp olive oil (or vegetable, if you prefer)
Half a chicken stock cube (optional)
150g button mushrooms, sliced
1 clove garlic, chopped
150ml double cream
1tsp Dijon mustard
Fry the chicken, salted, gently in the oil and butter. You may need less fat than I have suggested, because the chicken exudes its own. The oil helps to prevent the butter from burning.
When the thighs and drumsticks are golden (after about 15 to 20 minutes), pour in the water, and the half stock cube if using. (Some people don't like the taste of cubes; I think that, used cautiously, they add savouriness. Of course, proper stock would be better.) Cover the pan, and simmer gently for 30 minutes.
Meanwhile, fry the mushrooms and the garlic, with a little more salt, in the butter (I'd use about 25g) over a low to medium heat. If they exude a lot of liquid, turn up the heat to evaporate it. I usually judge them to be ready when the liquid has gone. Turn off the heat, and cover the pan.
Uncover the chicken. You may find that there is now quite a lot of liquid. Continue to simmer, gently, until the liquid is syrupy.
Pour in the cream and add the mustard, and allow the sauce to bubble and thicken for a minute or two. When you have the consistency you like, stir in the mushrooms, allowing them to warm through if necessary. Particularly if you have used a cube, you should not need more salt.