Roast rack of lamb with dukka

Dukka is an Egyptian nut and spice blend that varies from family to family. It can be sprinkled over rice or soup, and on pieces of warm pita dunked in olive oil it is one of the best nibbles to serve with drinks. It also makes an excellent crust for lamb. Some spice merchants now sell ready-made dukka, but I have given a recipe below because it is easy to make at home, and keeps well.