Wash the mussels in cold water,de-bearding if necessary. Discard any that are open.
Mash the red bean curd with a fork,then stir in the yellow bean soy sauce,stock and sugar.
Heat a wok until just smoking. Add the vegetable oil and,when hot,add the garlic and chillies and stir-fry until fragrant.
Deglaze the wok with the rice wine,then add the mussels and stir-fry for 2-3 minutes.
Add the capsicum and bean-sauce mixture to the wok and toss together.
Cover the wok with a lid or round metal tray and cook for 2-3 minutes,shaking the wok occasionally,until the shells just begin to open.
Use a slotted spoon to transfer the mussels to a bowl.
Return the wok to the heat and simmer the sauce,uncovered,until it reduces and thickens slightly.
Pour the sauce over the mussels and sprinkle with shredded green onion to serve.