Peel off and discard the outer leaves of the cabbage, then carefully peel off 4 good, bright coloured leaves. Drop them into a pot of simmering, salted water for 3 minutes, then drain and rinse under cold water. Shave off any inner ribs on the blanched leaves.
Trim the salmon fillets into neat squares, and remove any pin bones. Spread out a sheet of cling film on a work surface and lay