Chop lemongrass. Put in a food processor with ginger and garlic; whirl until minced. Scrape into a large bowl and stir in honey, soy sauce, and pepper. Add crabs and stir to coat well. Cover, then chill at least 15 minutes or up to 1 hour.
Pour oil into a 14-in. wok or a wide 8- to 10-qt. pot over medium-high heat. With a slotted spoon, add crabs (reserve marinade). Cover and cook, stirring often, 5 minutes (omit this cooking time if using fully cooked crabs).
Uncover pan, add marinade, and cook, stirring often, until crabs are steaming and meat is opaque, about 5 minutes.
Stir in cilantro and basil, then transfer crabs and juices to a serving bowl.
Note: Nutritional analysis is per serving.