Place pears, cinnamon, ginger and all but two teaspoons of the sugar into a saucepan. Add water, cover and gently bring to the boil. Simmer until the pears are cooked, but still a little firm. Cool, then mix in the nuts and spoon into six small, ovenproof dishes or one large dish, making the top as level as possible.
Crumble or grate the halva and spread it over the pear mixture, making it level as well. Sprinkle remaining sugar on top, then grill (note: grill=broil for americans) until the sugar and halva begin to darken (watch carefully as halva will darken quite quickly; it's best to grill under a moderate heat).
Stand a minute before eating. Serves 6.