Instant mashed potatoes. Put 1/2 cup in a Ziplock baggie; add bacon bits, grated cheese, a small spoonful of powdered milk and/or a little dab of butter. Add hot water to baggie; smoosh it around to mix it up. (Bonus: handwarmer!). Add salt & pepper. Eat from baggie; you don't even need utensils, you can just cut off a corner of the bag and squeeze it out

There are also ready-made instant Mashed Potato cups, but this way is a lot cheaper and customizable... plus you get to eat it by squeezing it into your mouth
(This recipe courtesy of the Calgary Area Pathfinders "Challenge the Chill" winter camp, 2008

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From my sister: Get dry
couscous from the bulk food store or a Middle Eastern grocery. Add 1/4 cup couscous to ~3/4 cup boiling water (or package directions). Cover it and let it fluff up for several minutes. (You can do this in a Ziplock baggie too, actually, but it's a bit messier than the mashed taters).
For breakfast: add sunflower seeds, brown sugar, dried fruit of your choice (cranberries and apricots are our faves), and top with unsweetened condensed milk or coffee cream. (This is now what I eat before centuries. Tasty, easy to eat and digest, and packs some serious calories, especially if you have as free a hand with the cream as I do...).
For supper: put in chopped dried sausage or jerky and 1/4 teaspoon of dried onion (or 1 tsp dried onion soup mix) at the same time as the couscous; add some dried veggies too if you like. A bit of hot sauce is a fine addition. The couscous with its additions should be easy to eat with a fork - its texture is similar to rice.
Couscous is a staple for us now on backpacking trips because it is so versatile, tasty, and (best of all) light to pack!!