Place the rice noodles in a large bowl and cover with boiling water; soak for 5 minutes only, then drain and rinse under cold water to stop cooking.
In a small bowl, whisk together tamarind puree, brown sugar, fish sauce, and oyster sauce until the sugar dissolves.
Heat the vegetable oil in a wok or large skillet over high heat until shimmering.
Add the minced garlic and sliced onion to the hot wok and stir-fry about 30 seconds until fragrant.
Add the minced chicken and cook, stirring, about 2 minutes until mostly cooked through.
Push the chicken to one side of the wok, pour the whisked eggs into the empty side, scramble until just set, then combine with the chicken.
Add the tofu, drained noodles, and bean sprouts, then pour the sauce over; toss gently for 1–2 minutes until the sauce is absorbed and noodles are heated through.
Stir in the sliced green onions and half of the chopped peanuts, toss briefly, then remove from heat.
Serve immediately topped with the remaining peanuts, lime wedges, extra bean sprouts, and a sprinkle of ground chili if desired.