Heat the olive oil in a heavy, medium saucepan. Add the rice and stir over moderate heat until coated with the oil. Add the orange muscat and cook, stirring, until it is completely absorbed. Add the nutmeg, cinnamon and 1/2 cup of the milk and cook, stirring constantly, until the milk is completely absorbed. Continue adding milk, 1/2 cup at a time, stirring constantly until it is absorbed before adding more. Cook until the risotto is creamy and porridgelike and the grains of rice are just tender. Stir in the sugar, vanilla and orange zest and transfer the rice to a bowl. Let cool slightly, stir in the beaten egg, then stir in the flour and baking powder.