Mix the dough. If using powdered masa harina, measure it into a bowl and add 1 cup plus 2 tablespoons hot tap water. Mix with hand, kneading until thoroughly combined. Cover and let stand 15 minutes. If using fresh masa, scoop into bowl. Break up and knead a few times until smooth.
Heat griddle or skillets. Set a large griddle (one that stretches over 2 burners) or 2 skillets on stovetop. Set heat under one end of griddle (or one skillet) at medium. Set heat under other end (or other skillet) at medium-high.
Adjust the consistency of the dough. Gently squeeze dough. If it is stiff (it probably will be), knead in water about 1 tablespoon at a time until the dough feels like soft cookie dough—not stiff, but not sticky. Divide evenly into 15 pieces and roll each into a ball. Cover with plastic or a damp towel.
Press out dough balls. Cut 2 squares or rounds of plastic bag a little bigger than the tortilla press. Open the press. Lay in one piece of plastic. Lay a dough ball in the center and gently mash with your fingers. Top with the second piece of plastic. Close the press. Press gently—enough to mash dough into 1/8-inch-thick disc about 5 inches in diameter. Pull off top piece of plastic. The edge all around should look smooth, not rough and cracked. Rough edges are a sign that the dough needs more water.
Unmold the uncooked tortilla. Pick up the tortilla by lower piece of plastic and flip it onto your right hand (if right-handed). IMPORTANT: top of tortilla should line up with top of index finger. Lay on medium-hot griddle (or skillet) by letting bottom of tortilla touch griddle, then lowering your hand slightly and moving it away from you—the tortilla will stick to the hot surface so you can roll your hand out from under it as it lies down flat. As the back of your little finger comes close to the hot surface, you’ll need to resist the temptation to jerk away, which inevitably leads to a crumpled up tortilla that has to be thrown away. I suggest you practice this whole unmolding step on your countertop before attempting it on a griddle or skillet. Once unmolded, simply roll the tortilla back into a ball and begin again. Masa is really malleable and easy to work with.
The first flip. After about 30 seconds, the edges of the tortilla will dry slightly and the tortilla will release from griddle—before this moment, the tortilla will be stuck to the hot surface. With a metal spatula (or callused fingers), flip the tortilla onto the hotter side of griddle (or hotter skillet). Don’t overbake the tortilla on the first side! If, when you flip it, the surface looks like dried mud with little fissures running through it, you’ve left it too long and the tortilla probably won’t puff.
The second flip. After about 30 seconds, the tortilla should be browned in spots underneath. Flip again. Cook for about 30 seconds more to brown that side. The tortilla should puff in places (or, if you’re lucky, it’ll balloon up like a pita; a gentle press with a metal spatula or fingers encourages puffing. Transfer to basket lined with towel.
Continue. Press and bake the remaining tortillas. Stack each baked tortilla on the previously baked ones. Keep the tortillas well wrapped in towel to keep them warm.
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