When it comes to survival food, pound for pound nothing beats pemmican. Pemmican happens to be the cornerstone of my food preps, and while I wouldn’t want to live exclusively on pemmican when the SHTF, living without it seems a lot worse.

Pemmican was invented by Native Americans to help them survive a long, cold winter when hunting opportunities were few and far between. Nobody knows exactly when pemmican was invented, but its documented history goes back hundreds and hundreds of years.
You can eat one square in the late morning, and it will tide you over and give you ample energy until later that evening when you start thinking about dinner. The caloric density is unequaled and for such a small quantity of food it really packs a punch. It doesn’t have to be a small quantity, but you’ll want it to be when you see how much it fills you up and how many calories it is.
I highly suggest you make your own pemmican, but before you do if you want to try it out, here is the best packaged pemmican product I’ve been able to find.

While it’s worth ordering a few of these to try them out, I can tell you with certainty that if you make your own it will be better in almost every way you can imagine. It will have a much longer shelf life, it will be more nutritious and it will be more filling. The product above would be good to experience what pemmican is like, but it is not cost effective to buy in bulk.
It consists of dehydrated meat often mixed with berries (blueberries or mulberries work best), and together they form a paste that hardens and has the consistency of a no bake cookie. It is somewhat chewy and somewhat dense. Typically a 1 inch by 1 inch square is all that is eaten, and that will satiate hunger for a good 6-8 hours. If you are experienced with intermittent fasting and going longer between meals than most people, one bar of pemmican can literally last you the whole day. No other survival food comes even close.
You can dry your thinly sliced pieces of beef or venison in the sun during the summertime. A much more efficient way would be to use a dehydrator though.