Heat the oil in a wok at high heat.
After a minute or two, throw in the garlic. It should only take a few seconds to brown.
Add the onion wedges and fry for a few more seconds.
Crack the egg and add it to the wok. Drop it from a low height to avoid splashing hot oil everywhere.
Stir to scramble the egg and fry for a few seconds. Keep occasionally stirring and/or rocking the wok from here on out.
Add the tofu and shrimp.
Add the noodles, then stir in the prepared sauce.
Add about half the water and keep stirring until it's reduced to a sticky sauce.
Try a noodle, it should be very close to done now. If not, carefully keep adding water until they are.
Add the garlic chives and mung bean sprouts, stir for no more than a minute.
Spread to bowls or plates and serve hot. Serve peanuts, lime wedges, and chili flakes on the side.