Mix the nuts and sultanas or currants together and spread the whole amount over 2 of the fish fillets. Put the lemon slices on top and then put the mint leaves on top of the lemon. Season with salt and pepper. Put a knob of butter in the centre of each fillet, then place the 2 remaining fillets on top.
Paint a sheet of filo pastry with melted butter and place one of the stuffed fish fil