Gaining

How to increase capacity and foods that keep a long time?

Hey all,
So I'm trying to fatten up, but I'm ridiculously tiny at the moment. I've tried to gain in the past but have two issues.

1. I have no time to cook which makes eating large amounts of food difficult.

2. I have a ridiculously small capacity. (like, I struggle to eat 2,500 calories in a day)

Which leads to dual questions:

1. Does anybody have any advice on how to up capacity? How can I make myself hungrier without getting my insulin incredibly out of whack and not spend loads of time eating? (I work an active job and don't have the "snack throughout the day option" a lot of people do)

2. Does anyone know good recipes or how to cook large amounts of food that last for a long time in the freezer or otherwise?

Thanks in advance!
6 years