Gaining

Heavy cream is great and all, but I don’t want to have gallons of heavy cream in the fridge that my roommates will see. Are there any good foods for gaining that don’t require refrigeration?

Also I’d rather have fatty foods over sugary ones

(I'm no expert but..)
If you've got a decent blender, or can afford one, I've just got into peanut butter shakes. using pure peanut butter (no sugar salt or palm oil added) from a supplements website where they sell protein powders etc. I blend with soy milk (long life) and sometimes add a banana or a scoop of huel.

Oils are some of the most calorically dense foods out there. Hence why fried food is so fattening.

A tasty, super high calorie snack is dipping a nice bread into an olive oil dip. You can make your own by sprinkling some parmesan cheese and italian seasoning into some olive oil.

You can easily soak up a half cup of oil with a small loaf of crusty bread. That's 1,910 calories in olive oil alone!!

Breads have lots of calories on top of that!