Combine rice, 1 1/2 cup milk, sugar and salt in a heavy pan. Cook over medium heat, stirring until thick and creamy – for around 15-20 minutes. Blend remaining milk and beaten egg and stir into rice mixture. Add raisins. Cook for 2 minutes longer, stirring constantly. Add butter and vanilla. Pour mixture into a serving dish, sprinkle with cinnamon and allow to cool.