Indian merchants introduced curries to Vietnam more than ten centuries ago. The Vietnamese made curry their own by adding their own flavors such as lemongrass and ginger. For this recipe, use the Vietnamese curry powder called Golden Bells. It's milder (less cumin and fennel seeds) and won't overwhelm the lemongrass and ginger. In case it's not available, I've included a recipe for a curry powder to make at home.
For a variations of this recipe, try yucca, taro, cauliflower, long beans and chayote. The recipe is adapted from the book, Pleasures of the Vietnamese Table, by Mai Pham. The Vietnamese curry recipe is from, A World of Curries, by Dave DeWitt.