Persian flour noodles (called reshteh, from the Persian for “thread”) are sold dried, or toasted and dried, at Persian groceries. They are made from water, flour and salt, and usually contain no eggs. Lacking Iranian noodles, you may substitute any flat, narrow, dried noodle, such as linguine. To toast noodles yourself, break them into pieces and toss them in a hot, ungreased skillet over low heat for a few minutes, until they are golden brown, or spread them on a baking sheet and broil them under high heat for 30 seconds. To cook 1 pound of dried noodles, bring 5 quarts of water to a rolling boil, add 2 tablespoons salt and the noodles, and cook for 2 to 12 minutes, depending on the width of the noodles. Test that the noodles have reached the texture you prefer by biting into one. Drain all the noodles. They are now ready for sauce.