Jif Extra Crunchy Peanut Butter: 16g fat, 7g carbohydrate, 7g protein.

Cheap, simple, convenient. I try not to over-think such things. As has been pointed out, for a couple of day's emergency rations, pretty much any calories you like and will eat when under stress will do.

PB has long been my back-up fuel of choice for backpacking, so I have confidence borne of experience that it will sustain my under heavy exertion if I "misunderestimate" my rations or ETA, and that it is palatable to me. I hoard the PB packets from MREs, or load my own.