Bring a pot of water to boil and turn off the heat. Soak noodles in hot water for 4-6 minutes, or until limp but still too firm to eat. Drain and then rinse well with cold water. Tip: Noodles must be under-cooked at this stage in order to come out right. They will finish cooking later when they are stir-fried.
Combine sauce ingredients in a small bowl. Stir well to dissolve the paste and sugar. (Note: If your tamarind paste is very thick, add 1 tablespoon of water at a time until the mixture is the consistency of a thick sauce. Note that this sauce should have a very strong flavor that tastes sour-sweet at first, followed by a salty and spicy taste. Set aside after mixing it thoroughly.
Warm a wok or large frying pan over medium-high heat. Add 1-2 Tbsp oil plus the white parts of the green onion (reserve the green for garnish), garlic, galangal or ginger, and sliced chili. Stir-fry for 1 minute to release the fragrance.
Add the broccoli, carrots, and 3 tablespoons stock to the wok. Stir-fry for 2 minutes, or until the broccoli is bright green and slightly softened. If the pan seems dry, push ingredients aside and add a little more oil in the middle; stir.
Add drained noodles, 1/3 of the sauce, and zucchini. Stir-fry everything together for 1-2 minutes using 2 utensils and a gently-tossing motion (like tossing a salad). Keep the heat between medium-high and high, reducing if noodles begin to stick or burn. Keep adding sauce a little at a time, and continue stir-frying for 3-6 minutes, or until noodles are soft but still chewy (al dente) and a little sticky.
Stir in tofu and any remaining sauce. Turn off heat. Add the bean sprouts, folding them into the hot noodles. Taste-test. Add more soy sauce for more salt/flavor. If it’s too salty or sweet for your taste, add a squeeze of lime juice. If too sour, sprinkle in a little more sugar.
Scoop noodles onto a serving platter. Sprinkle with reserved green onion, cilantro, and ground nuts. Add wedges of fresh-cut lime on the side. Serve immediately.
(Thai chili sauce can be served on the side for those who like their noodles extra spicy.)