Heat the oil in a large wok over high heat. Add the chicken and fry until lightly browned. Add the onion, mushrooms, zucchini and peas and toss until vegetables are softened. Add the rice, salt, soy sauce, ground pepper and tomato sauce and toss for about five minutes until the rice is coated and fragrant. Place rice mixture into baking dish.
Make the white sauce: stud onion with cloves, add along with bay leaf and milk to small saucepan and bring to a simmer on low heat, do not let it boil over. Remove from the heat. In a separate saucepan over medium heat stir together the butter and flour then gradually add the milk while stirring to a smooth sauce. Season with salt, remove from the heat and stir through the egg yolk and nutmeg.
Spread white sauce over the rice mixture. Top with grated cheese. Put under grill until brown. If rice mixture has cooled down use oven to brown off the top of dish. Sprinkle with chopped chives and serve.
Feel free to change combination of vegetables to suit your crowd. Try rice mixture for seasoning before adding it to baking dish.