To make the sauce: In a small saucepan, combine the palm sugar, water, tamarind paste, oyster sauce, fish sauce, and sweet soy sauce. Cook over medium heat, stirring occasionally, for 3 to 5 minutes, until the sugar has fully dissolved. Remove from the heat. (The sauce can be stored in an airtight container in the fridge for up to 1 week or in the freezer for up to 3 months.)

Soak the noodles: Place the rice noodles in a large bowl and add enough room-temperature water to cover them by 2 inches. Let soak until soft, about 4 hours. Keep the noodles in water until just before cooking to prevent them from drying out.

To make the pad Thai: Heat a large wok or skillet over high heat for 2 minutes. Reduce the heat to medium and then add the sunflower oil. Add the shrimp and cook, stirring occasionally, until the shrimp turn pink but are not yet fully cooked, 1 to 2 minutes. Push the shrimp to the side of the wok. Remove from the heat and add the shallots and tofu and cook, stirring frequently so the shallots cook thoroughly, 1 to 2 minutes. Add 1/3 cup of the sauce and stir to mix. Return the wok or skillet to medium heat.

Add the drained rice noodles. Increase the heat to high and mix everything together. Cook, stirring frequently, until the noodles are soft, 2 to 3 minutes.

Push everything to one side of the wok. Crack the egg into the empty side of the wok and let cook for 1 minute. Stir to lightly break the yolk but do not scramble the egg, then quickly move the noodles to cover the egg. This way the white and yellow parts of the egg will separate nicely. Cook, without stirring, for 1 minute. Remove from the heat. Add the bean sprouts, Chinese chives, and roasted peanuts and squeeze a lime wedge over everything. Stir again and transfer to a plate.