Soak the noodles in warm tap water for 20 to 30 minutes until pliable but still firm, then drain. Do not boil them. They finish cooking in the pan, and boiled noodles turn to mush the second they hit the sauce.
Stir the tamarind, fish sauce, and sugar in a small pan over low heat until the sugar dissolves. Taste it. It should be sour first, then salty, then sweet. Adjust until it is.
Pat the shrimp dry. Heat 1 tablespoon of oil in a wok or your largest skillet over high heat until smoking, sear the shrimp about 90 seconds per side, and remove.
Now cook in two batches, and this is the part that matters. Heat 1 tablespoon of oil, add half the garlic and shallot for 30 seconds, then half the noodles and half the sauce. Toss for about 2 minutes until the noodles absorb the sauce.
Push the noodles to one side, crack in 2 eggs, scramble until half set, then toss through the noodles. Add half the shrimp, sprouts, and chives, toss 30 seconds, and plate.
Repeat with the second batch. It takes 5 extra minutes and is the difference between pad thai and noodle soup.
Top with crushed peanuts and serve with lime wedges and raw sprouts.