Trim and seal the lamb cutlet than cook in the oven until medium rare, remove from the oven and brush with mustard. sprinkle the pistachios on the mustard, place in the oven for 1 more minute and than allow lamb to rest on a chopping board. Cut the prunes lengthwise and soak into the port for at least 1 hour. Slice the onion and sauté in salted butter and sugar until browned, add the prunes and toss until prune and well softened, add the spinach toss again and remove from heat. Use the same pan to reduce the port left from being absolved from the prunes together with the red wine until a sauce consistency. Slice the potato with the skin on and sauté in butter with the fresh thyme until nicely browned and cooked through. Cut large round three layered disks of filo pastry brushed with melted butter between each layer and sprinkled with black sesame seeds, bake at 180`c until lightly browned and serve as a garnish across the Lamb rack bones.