How can I create a varied (or at least tasty) menu for a 12 day hike whilst using as few ingredients as possible? I'm going on a 12 day hike with my boyfriend in a couple of months. We'll be at a mountain station that has limited supplies (e.g. meat) for sale every couple of days, but ideally I want to carry as much food as possible (buying food in the wilderness is expensive!). We'll be walking 15-20 kilometres a day. We'll be cooking food on a small gas burner (can only cook one thing at a time).

I've never hiked for more than 3 days before and I'm at a loss on how to plan to feed the both of us for that length of time. Whatever I bring needs to be low on weight/space taken up, and yet be high in energy and nutritional content. And preferably so that I can use the same ingredients for different meals. I don't want to bring something that I'm only going to use once.

I hope this is on topic here, because I would really need advice on what to eat, how to plan a menu/eating plan, how to make the food taste good with limited resources/time.
We take home-dehydrated cooked meat (beef, chicken, ground beef) along with spices, tomato leather to make tomato sauce, pasta, rice, dehyrated potato-and-sauce (eg scalloped potatoes) from the grocery store, home-dehydrated vegtables, and dried fruit. From that you can make stew, pasta-with-meat-sauce, curry-on-rice, and so on. You might also be interested in making your own english muffins since bread products squish and don't keep well: http://www.gregcons.com/canoe/muffins.htm. 

Backpacking is tougher than canoeing but as long as you can be sure of plenty of water, you should be fine with dried products. We usually bring a little frozen meat for the first night, and frozen bacon for the first morning, well wrapped in newspaper, but those might be too heavy when hiking.