Combine the black beans, soy sauce, rice vinegar and cracked pepper with water. Set aside. Heat the sesame oil in a large pan, add peppers and spring onions and fry for 30 seconds. Add garlic, ginger and mussels, cook for a further 30 seconds and stir in the black bean sauce. Cover the pan and leave on a high heat for three minutes. Stir when the mussels begin to open. Ladle the mussels and sauce into warm bowls, discarding any mussels that have failed to open. Finely chop the remaining spring onions to garnish and serve with fresh crusty bread.