Process together with the ground almonds, butter and parmesan.
Sandwich this mixture between two sheets of baking paper and roll out to a thickness of 5mm. Peel and slice the onions and fennel and sauté in the olive oil in a non stick frying pan. Add the rest of the olives and cook for about ten minutes, then season.
Steam the fish for 5 minutes, remove skin, then cover with the parmesan butter.