Most energy-dense options
Couscous and peanut butter are the most energy-dense vegan foods by both weight & volume that don't require cooking (excepting sugar, which is more energy dense but doesn't satisfy hunger).
Consider the following items:
- Peanut Butter
- dried fruit
- Spices (easiest are bullion cubes or the just-add-water soup packets)
Less-energy dense options
Less-dense vegan items (some that require adding boiling water):
- Ramen Noodles (can be eaten raw)
- "Quick-Cut" Oats
- Rice Vermicelli
- Parboiled Rice
- Dried Seaweed & Mushrooms
- (Dehydrated) miso soup packets/soy sauce
- dehydrated veggies (usually sold by the kilo for soups inc onion, tomatoes, peas, peppers, celery, green beans, parsley, etc)
And if you want fresh food, then you can sprout lentils by soaking them in an old peanut butter jar after you reach camp, draining & rinsing them in the morning, then letting them sprout in a sprouting bag hanging off your pack during the day.
You could also make chapati (flat bread) with flour, sugar, salt, water, oil. Flour & Sugar are more energy-dense than couscous, but this requires quite a sustained fire that will take much longer and use much more fuel (likely unavailable in an alpine environment) than the above options that can be rehydrated with cold water or just-boiled water.
Example food (per day)
When I (vegan) go trekking, this is usually what I bring per day (I buy these items in bulk, so I just measure them out into gallon ziplock bags by the handful. For reference, 6x handfuls of couscous is 200mL by volume):
- 200mL (~6x handfuls) of couscous
- 100 mL (~3x handfuls) of lentils
- 200g of peanut butter
- 1x dry soup packet
- 300mL (~5x handfuls) of raisins
- 300mL (~5x handfuls) peanuts
- 60mL (~1x handful) of rolled oats
- 1x tea bag
- 30 mL vegetable oil
If I'm only going for 2 days, I'll just double the above list. If I'm going for longer treks (eg longer than a week), then I'll add the occasional less-dense items (eg flour tortillas) to add some variety. After 3 days, it can be hard to throw down couscous & lentils twice-per-day.
I'll also have
- 1x chocolate bar
- Salt/black pepper mix
- dried red (spicy/picante) pepper flakes
You many not need that much food, but I do. I know a lot of people who plan on just having a snickers bar for lunch when they go trekking, and they expect to come off the trail a few kilos lighter than they entered. Personally, I have hardly any fat on my body, and I have a crazy high metabolism, so I pack way more calories per day than most people. YMMV.