There are many ways of cooking without electricity or gas. Some are fairly simple, others more complicated but most require fuel. A lot of fuel. Unless you have unlimited storage space to store fuel or other resources that make it feasible for you to do this, you may want to consider other alternatives.
Some of these alternative cooking methods are, cooking over a campfire or fire pit, propane or butane stoves, wood burning stoves, thermos cooking, sun ovens and many others. I think it might be a good idea to study all of them and decide which ones will work best for you. Yes, I believe you will need to be prepared to use several different methods.
One that is fairly new to me but which fascinates me is the Wonder Box cooker or the Wonder Oven. This is made using an 18 gallon rubbermaid tote (Another box or container of equal proportions will also work), and 2 cushions inside filled with polystyrene beads (like the bean bag chairs have.) The idea behind this cooker is that you cook or bake in water - water which you first bring to a boil, put your food inside and then cover and place inside the pillows inside the wonder box and cover. The food continues to cook or bake.
You can cook a whole chicken, bake bread, or do anything that you would want to do. The only fuel required for this method would be the fuel to bring the water to a boil. I am including some websites for instructions and a pattern to make your own wonderbox. I'm getting right on this bandwagon.
A friend tells me she baked bread (using 48 oz. tin cans to put her dough in) and it bakes perfectly. The wonder box will also keep cold food cold. It can keep ice cream frozen for up to 4 hours. I don't know about you but I think that being prepared (before you need to use it) would be a great asset to your food storage. The links below are for the cushion pattern and the construction instructions. Any questions, let me know and I can send you more info.
If you prefer to order the cusion already made here is a website where you can get more information: http://ecowonderoven.com/