Nine out of every ten people I know would define Pad Thai noodles as a spicy noodle dish made with shrimp, mung bean sprouts, and ground peanuts. But shrimps, mung bean sprouts, and peanuts are not the ingredients that define the Pad Thai noodle dish. The sauce makes the dish and it is called Pad Thai sauce. The dish doesn’t need to include shrimps or that chicken be present if shrimps are not. In Thailand, there are endless ways to serve Pad Thai noodles, some spicier than others, and there are versions that contain nothing but the noodles tossed in Pad Thai sauce and stirred with crisp mung bean sprouts and strips of scrambled eggs.
Pad Thai sauce is just a spicy version of sweet and sour sauce. Instead of vinegar, however, the sourness is derived from tamarind juice. Shaved palm sugar (panocha) is traditional but brown sugar will do the trick too.
To make Pad Thai sauce, simply mix tamarind juice (see how to extract tamarind juice, or you may use tamarind paste sold in jars), patis (fish sauce), shaved palm sugar (or brown sugar), and chopped chilis with just enough hot water to make the mixture stirrable. How much of each ingredient you should use depends entirely on you. Once you have your Pad Thai sauce, you can make your Pad Thai noodle dish. This is my version.
Heat the cooking oil in a pan. Add the chicken strips and cook until the edges start to brown. Add the ginger, garlic, and onion (or shallots). Stir fry for about 30 seconds. Add the vegetables. Stir fry for another 30 seconds. Season with fish sauce. Stir. Add the noodles. Stir. Pour in just enough Pad Thai sauce to wet the noodles. Stir and toss to mix everything. Transfer to a serving platter. Sprinkle with chopped peanuts and fresh cilantro or parsley. Serve hot.