Place the chopped cabbage in a bowl and sprinkle with the salt.
Let the cabbage rest for 10 minutes to release moisture.
Squeeze the cabbage firmly to remove excess liquid, then transfer to a clean bowl.
Add the ground pork or chicken, green onions, ginger, garlic, soy sauce, sesame oil, rice vinegar, and black pepper.
Mix gently until just combined.
Cover the filling and refrigerate for 15 minutes.
Bring a large pot of salted water to a boil.
Blanch the whole cabbage leaves for 2 minutes until pliable.
Transfer the leaves to a towel and trim the thick center rib.
Place 2 tablespoons of filling near the base of each leaf.
Fold in the sides and roll tightly into compact bundles.
Place the cabbage-leaf dumplings seam-side down in a shallow pan.
Add the broth to the pan and cover.
Simmer gently for 10 minutes until the filling reaches 165°F.
Serve warm with broth spooned over the dumplings.