Other than things already mentioned I sometimes use instant mashed potato. I stick to 'Mr Mash' rather than Smash, much better taste but it does benefit from butter, salt, dried chives and what have you to improve the flavour.
I like the 'Mug Shots' snacks, some of those are pretty good with a few additions. The cheesy pasta ones are great, 2 packs with chunks of salami added and real cheese fills a solo cooking pot and hits the spot a treat.
Packet soups that take a few minutes of simmering are much better tasting than instant ones if you're making it into a full meal by adding meat and mashed spud.
Someone already mentioned tortillas, if you can get them go for the soft ones (made by Discovery I think), they cope better with being rolled up cold. Some kinds crack and snap, still edible but more awkward.
Never underestimate biscuits and chocolate!
Of course if you carry a small frying pan you can carry eggs, bacon and sausage for the first couple of days after resupply. Otherwise pies are pretty calorie dense if you don't mind the weight for the first day or so.