Leave mussels in a bowl of cold water for 15 minutes, then strain. Discard open mussels. Rinse remaining mussels in cold water until all traces of sand are removed.
Place wine, peppercorns, clove and bay leaf in a large saucepan and bring to a boil. Add mussels, cover and cook 5 to 10 minutes until they open. Strain; discard any closed mussels. Remove mussel flesh from open shells and allow to cool completely.
Halve tomatoes, remove seeds and cut into small strips. Cut yellow capsicum into small cubes. Thinly slice zucchini. Peel shallots and slice. Remove hard stems from rocket and chop leaves. Place mussels and all prepared salad ingredients except rocket in a bowl and mix together.
To make vinaigrette, whisk oil, lemon juice, tomato juice, dried chili flakes and sugar until combined; add salt and pepper to taste. Drizzle vinaigrette over salad.
To make croutons, cut bread into cubes. Heat butter in a nonstick pan and lightly fry bread cubes over medium heat, turning often and taking care that they do not burn. Spoon salad into bowls, top with rocket and croutons.