Make the Sauce: Whisk together all the ingredients in a bowl and set aside.
Make the Prawns: Cut down the backs of the prawns and remove the black intestinal vein. Set aside.
Heat the oil in a wok or shallow saucepan over high heat. Add the garlic and stir-fry for 1 minute. Add the chiles and stir-fry for another minute. Add the prawns and stir-fry until the shell turn slightly red, about 2 to 3 minutes. Add the sauce and stir-fry until the shells turn red.
Break the egg into the wok and, using a fork, streak the egg through the sauce (this is an important step, as the egg has to be in beautiful gold and white streaks). Simmer the sauce for a few seconds and remove from the heat. Stir in the scallions and lime juice.
Transfer the prawns to a platter, garnish with the cilantro, and serve with chunks of French bread.
Note: This dish is also wonderful with mussels, crabs or lobsters; or you could mix all the seafood together. It's a Singapore version of a French seafood stew.