1. Place a large casserole over a high heat and bring the stock, wine, onions and thyme to a simmer.
2. Add the chicken and bring back to simmering point.
3. Add the mushrooms and continue to simmer for about 15 - 20 minutes, or until the chicken is cooked through.
4. Remove the pan from the heat, lift out the chicken and leave to cool slightly before removing the chicken from the bone.
5. Whisk the egg yolks and cream together in a bowl and add gradually to the casserole, mixing well as you pour.
6. Return the chicken to the pan and season to taste. Serve with boiled rice and a parsley garnish.