If you have a food processor, add einkorn flour, salt and cubed unsalted butter. Pulse until mixture resembles coarse, crumbly sand. To combine by hand, add the three ingredients to a large mixing bowl and use a pastry cutter to work the mixture until well incorporated. Pea sized crumbs are okay, but the smaller the better.
In a small bowl, stir together the warm water and sourdough starter.
Add the flour mixture to a large bowl and make a well in the middle to pour in the sourdough starter mixture. Work the dough until it forms a ball that no longer feels sticky. If the dough is sticky, add a small amount of flour one tablespoon at a time.
Knead the dough by hand or in a stand mixer on a low speed for three minutes. The dough will feel very soft.
Use the same bowl that the dough was mixed in to let the tortilla dough raise covered in a warm area for a minimum of two hours. For a long fermentation, place the covered dough in the refrigerator for 12-24 hours.
When ready to bake, preheat a cast iron skillet to medium heat. The skillet should be very hot but not quite smoking.
Divide the dough into an even amount of balls. For easy reference, 12 dough balls will make approximately thee inch tortillas, while 6 dough balls will make approximately eight inches tortillas. I am making 8 six-inch tortillas today. The goal is for the tortillas to be as thin as possible.
Use a tortilla press to shape the tortillas. I do not have a press, so I used the bottom of a heavy pan to flatten my dough balls. Using parchment paper to sandwich the dough will make life so much easier!
These tortillas cook fast! Using the preheated skillet, cook each tortilla for about thirty seconds on each side. The tortilla will puff up slightly and release easily from the skillet. If the tortillas are becoming too brown or blackened, turn the heat down and take a break until the skillet cools a bit.
Serve the tortillas warm and fresh. Tortillas can be stored at room temperature for up to 3 days or refrigerated for up to one week.