Put the noodles in a pot of water on the stove, bring it to a near boil, then remove from heat and set aside.
In a bowl, add the fish sauce, tamarind paste and water, chili sauce, and brown sugar. Set the pad Thai sauce aside.
In a small bowl, places the slices of chicken and pour the cornstarch/soy sauce mixture over the chicken. Mix well and set aside.
Drain and rinse the noodles with cold water and set them aside.
In a wok over medium-high heat, add 2 tablespoons of oil and the garlic and stir-fry for 30 seconds. Add the chicken and marinade and stir-fry for a minute. Add the chicken stock and tablespoons at a time, enough to keep the chicken cooking, continuing until all of the stock has been added, cooking for a total of 5 to 8 minutes.
Add the noodles, pad Thai sauce, and toss the noodles with 2 spatulas or spoons for 2 minutes.
Add the black pepper and bean sprouts and toss for another minutes. Taste to test the seasoning; you may need to add another tablespoons of fish sauce.
Serve by topping the noodles with the spring onion, coriader, and nuts. Add the fresh lime wedges and serve with a bottle of Thai chili sauce on the side.