Preheat the oven to 130C/250F/Gas 1.
To make the herb crust, lay the ciabatta, lemon zest, capers, anchovies, onions and olives on a baking sheet. Place them in the oven to dry out for 1½ hours.
Transfer the mixture to the bowl of a food processor fitted with the metal blade and blend with the basil and parsley until fine breadcrumbs form (about two minutes).
Turn the oven up to 210C/410F/Gas 7-8. Heat a large heavy based frying pan, and sear the lamb on all sides until brown, starting on the side with the fat.
Brush the fat side of the lamb with mustard so that it is well covered and then roll it in the breadcrumb mixture to form the herb crust. Place the meat in a shallow roasting dish and bake in the oven until medium rare, about 15-20 minutes.
Remove from the oven and leave the meat to rest. Add the beef stock and a splash of red wine to the roasting tin to deglaze it and create a sauce. Season to taste with salt and freshly ground black pepper.
To serve, cut the lamb rack into cutlets.
Drizzle the sauce around the outside of each plate and serve.