Bring a large pot of water to a boil and blanch the cabbage leaves for 2 minutes until pliable, then immediately shock in ice water and pat dry.
In a medium mixing bowl, combine the ground beef, diced water chestnuts, sliced green onions, grated ginger, minced garlic, half of the tamari, sea salt, and black pepper.
Lay each blanched cabbage leaf flat on a clean surface and trim the thick part of the central rib if necessary to make rolling easier.
Place approximately 2-3 tablespoons of the beef mixture at the base of each leaf, then roll tightly while tucking in the sides.
Place the rolls seam-side down in a steamer basket set over a pot of simmering water.
Cover and steam for 15 to 18 minutes, or until the internal temperature of the beef reaches 160 degrees Fahrenheit.
In a small bowl, whisk together the remaining tamari, toasted sesame oil, and rice vinegar to serve as a dipping sauce for the warm rolls.