Preheat the oven to 200C/400F/Gas 6.
Season the chicken with salt and freshly ground black pepper, then cook skin-side down in a hot pan for 4-5 minutes, until the skin is crisp and golden-brown.
Turn the breast over to cook for one minute, then transfer to a deep ovenproof dish, skin-side up.
Add enough chicken stock to come a third of the way up the chicken. Place into the oven and cook for 20-25 minutes, or until the chicken is completely cooked through.
Meanwhile, melt the butter in a frying pan. When the butter is foaming, add the mushrooms and fry for 3-4 minutes, until golden.
Add the white wine and boil for 2-3 minutesto reduce the liquid almost completely.
Add the cream, spinach and tarragon and boil to reduce the liquid by a third.
For the rice, place the cooked rice into a bowl, add the nuts and butter and mix together well.
To serve, spoon out a portion of rice mixture onto a plate. Place a chicken breast alongside and spoon over some of the cream sauce.