Place noodles in a bowl, cover with boiling water. Soak 5 minutes, then drain and rinse under cold water.
Mix tamarind puree, brown sugar, fish sauce, and oyster sauce in a bowl.
Heat vegetable oil in a wok over high heat. Add garlic and onion, cook 30 seconds.
Add chicken, cook 2 minutes until mostly cooked through.
Push chicken to one side, pour eggs on the other. Scramble, then mix with chicken.
Add bean sprouts, tofu, noodles, and sauce. Toss gently for 1–2 minutes until sauce is absorbed.
Add green onions and half the peanuts. Toss quickly, then remove from heat.
Serve topped with remaining peanuts, lime wedges, and extra bean sprouts. Sprinkle with chili if desired.