Blanch the napa cabbage briefly in boiling water, then cool in cold water and squeeze out the excess water.
Drain the tuna using a sieve to remove any liquid.
Wrap the tofu in a cloth and squeeze thoroughly to remove water, then mash it.
In a bowl, add napa cabbage, tuna, tofu, salt, and pepper, and mix well.
Wrap the filling with napa cabbage instead of dumpling wrappers.
Place the dumplings in a steamer and steam for 10 minutes.