Using a sharp knife, slice the skirt steak as thin as possible. In a airtight storage bag, add milk, olive oil, yogurt, garlic, salt, and pepper. Add the prepared meat and keep and then let marinate in the fridge for at least 4 to 5 hours or overnight.
The next day, cover a work surface with two large pieces of plastic wrap. Remove the beef from the fridge. Place a layer of the beef flat onto the plastic wrap, making a rectangle that is about 10-inches wide. Make another 2-3 layers of beef evenly on top of the first until all beef has been used. Starting at the bottom edge, begin rolling the beef together up to the top of the plastic wrap, creating a large sausage shape. Twist each end of the plastic wrap closed like a candy wrapper, adding an additional piece of plastic wrap if necessary. Then, tie each side with a piece of twine so it is firmly closed. Place in the freezer for at least 4 hours.
Transfer the frozen beef into the fridge two hours prior to cooking. We do not want it to thaw fully but be easier to slice thinly when needed.