1. Melt the butter and sauté onion, green peppers, and garlic. Add mushrooms and fry until tender.
2. Stir in the flour to form a roux/paste and add the chicken stock and milk and bring to the boil.
3. Keep stirring until sauce thickens. Add the cooked chicken and seasoning and sherry. Heat through before serving. Chicken a la king can be served with mashed potatoes, pasta or rice.