Gaining

Heavy cream has little to negligible lactose. Usually with dairy the higher the fat the less lactose. But that's not true of all. Also, hard cheeses, like cheddar also have pretty much no lactose. I find heavy cream works wonders. You should still pace yourself and work your way up in what you take in a day. As it can still bother the digestive track because of how much fat it has in it. Drinking it or cooking with it in small amount many times thru the day is better than taking a lot all at once. You can probably find how much, if any, lactose is in various dairy thru Google.

Lactaid tablets can give you the enzyme to digest lactose. Barring all the previous, coconut cream has almost the same amount of fat and calories with no lactose. If you like the taste of coconut. I have issues with lactose and have found heavy cream to be fine and work very well. Hope that helps, best of luck!

One of the speculations as to the effectiveness of heavy cream is the high amount of stearic acid relative to other sources of fat.

So ghee/clarified butter should still have that fatty acid, with negligible lactose

Cacao butter actually has quite a lot of stearic acid! About a third by weight, IIRC