Despite its common name of Vietnamese mint (or hot mint), rau ram is not related to the mint family, but is actually a member of the buckwheat family. Rau ram has long, smooth green leaves on a purple tinged stem. Its aroma is described as a combination of lemon, coriander, and cilantro with a bitter, peppery flavor. If you cannot locate rau ram, you can substitute ordinary mint.
These and other great recipes are from The Culinary Institute of America's cookbook, One Dish Meals.