Corn tortillas are made with a type of specially treated corn flour called masa harina. To make masa harina, whole corn kernels are boiled with an alkali until the hulls loosen and float to the top. The kernels are then drained, crushed, and dried. The resulting flour is mixed with water and kneaded into a pliable dough in order to make tortillas. You can find dry masa harina at many supermarkets. At specialty stores and Mexican grocers, you may even find fresh masa, which needs to be used right away.
Even though they're such a simple item, it takes years of practice before cooks can effortlessly make a perfect tortilla. (A tortilla press makes flattening the rounds much easier.) For corn tortillas, divide the dough into small balls--about the size of a walnut. Keep the dough wrapped in plastic while you work with one piece at a time.
The best way to bake the tortillas is to use a cast iron griddle--the kind that stretches across two burners of your stove. Two cast iron skillets will work, as well.
* Heat one burner to medium-high and one to medium. There's no need to add oil to the pans: you aren't frying the tortillas, just heating them until the dough is cooked but they're still pliable, not crisp.
* If you have a tortilla press, flatten the dough and begin baking. If you're using your hands, the easiest way to flatten the masa balls is to use a gallon-sized plastic freezer bag to prevent the dough from sticking to the counter.
* Flatten the dough in between the sheets of plastic into a round as thin as you can make it without tearing. Peel it from the plastic and transfer it to the hottest griddle.
* To lay the tortillas in the pan, your knuckles will be close to the heat source, but don't panic: working from left to right, lay the left-hand edge of the tortilla onto the griddle, and gently sweep your hand away--don't jerk it. The edge of the tortilla will stick to the griddle, so as you move your hand, the tortilla will fall into place in the pan.
* After about a minute on the hot griddle, flip the tortilla over into the cooler skillet.
* Using tongs--or your fingers, if you're brave and heat-tolerant--gently touch the center of the tortilla until it starts to puff slightly.
* The tortilla should be done, developing brown spots, after 30 seconds to a minute.
* Wrap the hot tortillas in a clean kitchen towel while you shape and bake the rest of the dough.