Cut the chokos under running cold water. remove peel and discard core. Cut into cubes and drop into boiling salted water for 5 minutes. Drain and cool. Cut nashi in to like sized cubes. Squeeze over lemon juice and combine with cooked chokos. Heat oil in wok and stir fry beef for a couple of minutes. Cook in several batches to allow beef to brown. Remove beef with a slotted spoon and fry the spring onions, garlic, ginger and macadamias on the same oil and juices for 1 minute. Combine the water, corn flour soy and chilli sauce and add to the pan along with the beef and stir until thickened. Add the chokos and nashi, stir just to mix and serve immediately. Garnish with sesame seeds.