In a large ovenproof skillet or medium saucepan, brown the onion in 45 ml (3 tablespoons) of butter. Add 2 peeled and sliced carrots, 2 chopped stalks of celery, 1 finely chopped garlic clove and sauté for about 2 minutes. Season with salt and pepper. Add 500 ml (2 cups) of long grain rice and stir to coat with the butter. Add 750 ml (3 cups) of chicken broth, 500 ml (2 cups) of diced cooked chicken, 125 ml (1/2 cup) orange sauce and stir to blend. Cover and bake in the middle of the oven at 180 °C (350 °F) for 30 to 35 minutes or until the rice is tender. Add 125 ml (1/2 cup) chopped parsley and the grated zest of 1 orange. If you do run out of orange sauce, replace with 60 ml (1/4 cup) of chicken broth with 45 ml (3 tablespoons) of marmalade.