Clean the crabs, remove the shell and cut into half. Heat oil in a wok and deep-fry crabs for 1 minute. Dish out and drain.
Remove the oil, leaving only one tablespoon in the wok. Add ginger and fry until fragrant. Pour in the wine and add the remaining sauce ingredients. Bring to the boil, then reduce the heat and simmer for 2-3 minutes. Keep stirring the sauce to prevent it from burning.
Add the crabs and stir briskly to coat the crabs with the sauce. Reduce the heat and simmer until the sauce thickens. Dish out and serve.