ANZAC biscuits!
The iconic favorite of Australia and New Zealand. Kind of like a homemade granola bar -- it's a treat, it's nutritious, and reasonably shelf stable.
The story goes that, during the First World War, wives and girlfriends would bake ANZAC biscuits to send to their soldiers posted abroad. The biscuits had to be tough and non-perishable to survive the journey by ship with no refrigeration.
Everyone has their own variation of the recipe, but the primary components are: rolled oats, flour, sugar, and coconut -- which are all fairly stable, especially if kept sealed and airtight. The other ingredients (margarine, baking soda, and water) are more perishable but are used in small amounts. And, the biscuit is baked until it's pretty much dry (and I suppose sterilized). The texture can be made anywhere from soft(-ish) and chewy to hard as nails. The stiffer the biscuit, the longer they last. Sealed in a zip-lock bag they can stay good for weeks.
One special ingredient is required that might be unfamiliar here in the States:
golden syrup (syrup from processed sugar cane, kind of akin to molasses). There are (arguments abound) satisfactory substitutes but, If at all possible, I recommend using real golden syrup -- it has a toasty/buttery aspect that really makes the flavor. Look for Lyle's Golden Syrup (in the can with the dead lion surrounded by insects, yum!) I have found it at Safeway, but Amazon carries it if all else fails.
ANZAC biscuits at wikipedia
Oh yeah, they call 'em
biscuits but they're really
cookies.