Fennel and dill resemble one another since both have soft needle-like leaves which enable people to confuse them with each other.

The same might go for the celery and dill-looking hybrid you've seen listed in ingredients for soups and salads: what is fennel? It's not celery or dill, but surely you've thought it looked like ...

Bring to a simmer for 5 minutes. Add the leeks and fennel to the simmering stock. Add the chopped dill, stems, cavolo nero, and more soy sauce to taste, if needed. Simmer for another 2–3 minutes ...