First buy some baking potato's, you can usually find them at your local grocery store, and when you get it home, stab a fork into it a couple of times, (this is to let the heat penetrate and allows it to cook more evenly). Then put it in a preheated 350 degree oven for approx 1 hr. Then take it out of the oven and put it on a plate. Take a sharp knife and and put a deep slice down the middle, don't cut it half, just cut it deep on one side without actually cutting it in half. Then add salt and pepper to taste.
Keep in mind however, this is not a recipe for the faint-hearted, its a bold and somewhat risky and complex recipe that only experienced cooks should attempt. I have successfully done this recipe a few times. So go at it with caution, be careful while preparing it.