Corn tortillas start with masa harina, which is corn tortilla flour made from sun-dried corn kernels. Look for masa harina at a Mexican grocer or in the Mexican ingredients aisle of your grocery store. Flour tortillas usually start with all-purpose flour.
To start, place the masa harina or all-purpose flour in a medium mixing bowl. Using your hands, mix together the masa harina or flour with enough water to make a firm but moist dough that is a nice rolling consistency -- kind of like children's modeling clay.
Tip: If the dough is dry and crumbly, knead in more water, 1 tablespoon at a time.
Once you're happy with the consistency of the dough, let it rest for about 15 minutes to even out the moisture and make the dough easier to roll.
Use your fingers to divide the dough into 12 even portions, and roll them into balls.
Place one ball between two pieces of waxed paper that are about 7 inches square. If you have a tortilla press, now is the time to pull it out. Otherwise, a rolling pin works fine.
With the tortilla press or rolling pin, flatten the dough ball into a 6-inch circle between the waxed paper pieces. Repeat this shaping step with the remaining balls.
Tip: Keep the waxed paper in place until cooking time to keep tortillas from drying out and for easier transport.
Carefully peel off the top sheet of waxed paper and place the tortilla, paper side up, on a medium-hot ungreased skillet or griddle. As the tortilla begins to heat (this should take about 20 seconds), peel off the remaining sheet of waxed paper.
If you're making corn tortillas, cook each one for 2 to 2-1/2 minutes, turning occasionally, until the tortilla is dry and lightly toasted. (Note: Corn tortillas do not brown much.)
If you're making flour tortillas, cook each one for 20 to 30 seconds or until puffy, and then turn and cook until the edges curl slightly.
Make-Ahead Directions: Tortillas freeze well for up to 1 month. Stack them, separated by two layers of waxed paper, and place in a freezer bag and freeze. Thaw before using.