Prepare all the ingredients.
Take the chicken thighs, break the bone at the joint...
... then using a knife, remove the bone of the thigh taking care to leave the skin attached to the bone.
Reserve the chicken flesh.
Stuffing: Remove the skin of the belly...
... and cut it into pieces.
Roughly mix using a mixer.
Repeat with the chicken flesh.
Mix the meats in a pan.
Add the egg, cognac, salt and pepper.
Take the thighs once again. Place the skin on the working surface, reshape the thigh using the stuffing.
Fold back thoroughly the sides of the chicken skin.
Wrap one after another the thighs that were reconstitued with aluminium foil.
Place them in a baking pan with a bit of water and bake 40 mn at 160°C.
Meanwhile, roughly chop the button mushrooms. Sweat the mushrooms in butter.
Add the crème and season.
When cooked, remove the aluminium foil.
Serve hot with a mushroom duxelle.