Pad Thai is a popular Thai noodle dish that is typically made with thin, flat rice noodles. The noodles are soaked in boiling water until they are soft and pliable, but not overly soft, and then stir-fried with other ingredients. Other common ingredients in Pad Thai include bean sprouts, garlic chives, scrambled egg, firm tofu, and a protein such as chicken or shrimp. The dish is typically seasoned with a sweet-savory-sour sauce that includes ingredients such as fish sauce, vinegar, sugar, and tamarind paste. However, if tamarind paste is not available, rice vinegar or ketchup can be used as a substitute. To make vegan or vegetarian Pad Thai, the egg can be left out and the fish sauce can be substituted with more soy sauce.