1. Bring a large pot of water to boil, then remove from heat. Dunk in the rice noodles. Soak (do not boil) the noodles until soft enough to eat, but still firm and a little crunchy. Drain and rinse the noodles thoroughly with cold water. Set aside.
2. In a small bowl or cup, dissolve the tamarind paste in the hot water. Then add the other sauce ingredients, stirring well. Adjust seasonings to your taste. Set aside.
3. Heat a wok over medium-high heat. Add 2 TBSP of oil, then add the shallots and garlic. Stir-fry 1 minute.
4. Add the shrimp plus 2-3 TBSP of chicken stock. Stir-fry 2-3 minutes, or until shrimp are pink and plump.
5. Push ingredients aside, making room in the center of your wok/pan. Add 1 TBSP of oil, then crack in the egg. Stir-fry to scramble (30 seconds to 1 minute).
6. Add the drained noodles and drizzle over the pad Thai sauce. Use 2 utensils and a gentle "tossing" motion to stir-fry everything together. Keep the heat between medium and medium-high; you want your pan hot enough to cook the noodles, but not so hot that the bottom of your pan burns. Stir-fry 4-6 minutes, or until noodles are chewy and a little bit sticky.
7. Remove from heat and adjust seasoning to your taste.
8. Top with the scallions, cilantro, and peanuts, and garnish with lime wedges.