There's about 150-200 calories in a normal sweet red bean paste bun. If you multiply that by 10 you'd get around 2000 calories. Or, around 2x of a normal chipotle burrito.
Let's not get started with custard, white chocolate, dark chocolate... etc.
If you say that magic negates the effects of sugar and carbohydrate, then what is the point of eating it? It would not taste good, and it would not give you energy. It would just fill you up with nothing to show for it.