Heat the oil in a frying pan and fry the mushrooms for 3-4 minutes, add the rice, walnuts and chicken and fry for 2-3 minutes until heated through, season to taste and stir in the parsley and 2-3 tbsp water.
Cut the tops off the peppers and remove the seeds. Trim the bases if needed so they stand upright and place them in a small roasting tin with 3 tbsp water in the base.
Spoon the rice mixture into the pepper shells and bake for 30 minutes or until the peppers are just softened. Serve with a fresh leafy salad.
You can use this filling to stuff large onions or aubergine shells. Try replacing the chicken with shredded pulled pork.