Place rice noodles in a large bowl and cover with boiling water. Soak until softened, erring on the side of under-cooked. Drain and rinse under cold water.
Combine tamarind, sugar, fish sauce, and oyster sauce in a small container. Set aside.
Heat oil in a large pan over high heat. Briefly fry garlic and onion.
Add chicken to pan and fry until mostly cooked through.
Push contents of pan to one side. Crack eggs into other side of pan and scramble. Fold scrambled egg into onion and chicken.
Add bean sprouts, tofu, noodles, and sauce. Toss gently until sauce is absorbed by the noodles.
Add garlic chives and half of the peanut, tossing to combine.
Serve immediately, sprinkled with remaining peanuts and accompanied by lime slices.
Made a double batch (didn't double fish sauce). Omitted chicken and added ~400g tofu instead (added tofu after frying onions). Omitted garlic chives, instead doubling garlic. Forgot to add half the peanuts to the dish, so wasn't as peanut-y as usual, but still very good. Could have used more fish sauce, but maybe not the full 4 Tbsp.
Made a double batch with chicken breast; no bean sprouts; 3 Tbsp. fish sauce. This is very good, the best iteration of this so far. Perhaps a tad too sweet, but with chile flakes just right.