Gain weight with bentos

I know lots of people use bentos as a healthy and tasty way of losing weight, and I think that's great. But some of us have the opposite problem, we need to put weight on (don't be jealous, it aint good!). Ok so I could make one HUGE bento or just go to Mcdonalds instead, but seriously I can only eat so much and I want to do it healthily! Does anyone have any good ideas for putting weight on healthily with bentos?
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