Fennel contains a component of aniseed oil, which has a distinctive tangy odor. If blanched, it loses this flavor. In order to maintain the unique flavor of fennel, when making dumplings, it is recommended to chop the fennel a little bit and put more oil in it to prevent it from getting watery. The fennel dumpling filling will be more delicious after this treatment.

And blanching requires extra steps and time, while without blanching you can just chop the fennel and mix it with the rest of the filling, which is much easier and faster.