We took my father in law out for dinner yesterday to our favorite Italian joint. I had two appetizers for supper (I often like to do that): Carpaccio, and the steamed PEI mussels in Green Harissa.
Well, that harissa/mussel broth was the tastiest new flavor I've tasted in a year. Wow. Luckily for me, there was no cilantro in it (I am among those for whom cilantro tastes like gasoline).
There are many variations on Green Harissa - you can google them. It's not meant to be overly hot, just tangy. As best I can tell, this one contained jalapenos, garlic, mint, scallions, black pepper, salt, flat-leaf parsley, olive oil, lemon zest, a little sugar. Some water. No spices, because the mussel broth had plenty of good flavor. Mix raw in blender or immersible blender.
For vegetables or fish, you might want to use some of the spices the recipes suggest.
Photo is farmed mussels, Nova Scotia