Cook the potatoes in their skins in a pan of boiling salted water for 15-20 minutes or until just cooked.
Peel a potato and slice crosswise into 4. Brush 3 sheets of filo with olive oil and arrange overlapping but at angles to one another. Lay the potato slices in a row across the centre and put a teaspoon of pesto on top of each slice. Put a red mullet fillet on top, skin side up, season with salt and pepper and fold the pastry over, wrapping loosely as if making a parcel.
Put on an oiled baking tray. Make 3 more parcels in the same way, transferring them to the tray when done. Melt the butter and brush them all over with it.
© 1995 Alastair Little. All rights reserved.