You need slow and steady heat to evenly cook the brulee, which is why it also needs to be shallow. If you bake it, chill it, and try to re-bake it, the eggs will cook more than you want them to, and you get a curdled mess.
One case where this works, though, is a double layer brulee. Bake a thin layer of choc. brulee, chill, and pour on a thin layer of vanilla. Bake again. The top layer, along with the water bath, seems to insulate the bottom layer, and because the vanilla is so thin, it doesn't require full baking time. It helps to cover the ramekins with an inverted sheetpan.