Preheat the oven to 180°C.
Set the two fleshier pieces of salmon aside and dice the tail piece.
Blend the salmon tail, shallots, cream, aniseed, egg, and parsley into a smooth paste.
Mix the small raw prawns into the blended salmon mixture.
Rub pastis over the salmon pieces, make a 1cm deep cut in each, and spread the mixture over the cut side.
Fold each salmon piece in half to enclose the filling and tie with string.
Fry the salmon parcels and garlic in butter in a roasting tin until browned.
Roast the salmon in the oven for 7-8 minutes.
Add Mediterranean prawns to the tin and roast for another 7-8 minutes until cooked.
Stir-fry the onions and Brussels sprouts in smoking hot oil for 2-3 minutes.
Slice the salmon parcels and serve with the prawns, sprouts, and fresh parsley.