I cooked my mussels seperately in water then added them to the wok to toss in sauce and heat through. My mussels were very dirty with thick beards so I removed and cleaned them as best I could and cooked them seperately so I did not end up with any grit in my stir fry. That and there is not much liquid to cook them in the sauce, if using smaller mussels you could add these to the wok and cover with a lid and they will open. I had very large mussels from Spain as that was all that was available. but I have to say were delicious compaired with the usual ones I buy.