For the juice: Heat the water in a small pan and add the ginger pieces. Bring to the boil, add the rock sugar, and let the juice simmer over low heat for 5 minutes, before serving.
For the sauce: Add the water, ketchup, soy sauce, sugar, and cornstarch, to a bowl, and mix well. Set aside.
For the crab: Heat a wok over a high heat and add the groundnut oil. Add the garlic, ginger, chiles, and stir-fry for 30 seconds. Add the crab to the wok and stir-fry for an additional 1 to 2 minutes. Stir in the chile sauce, and cook for 1 minute, then add the water and lime juice.
For the egg noodles: Combine the noodles and the chile flakes and adjust their seasonings with the soy sauce. Toss the ingredients, and then stir in half of the spring onions and half of the chopped cilantro.
To serve, plate the crab with the egg noodles and top with the remaining spring onion slices and cilantro. Serve immediately with a shot glass of Ginger 'Juice.'
*Can be found at specialty Asian markets. Tip: You can serve this recipe as a starter without the addition of the noodles and I like serving this dish washed down with some homemade ginger juice - which is a real balance of "Yin" and "Yang" as crabs are "Yin" and ginger is "Yang".