Soak the cucumbers overnight. Cover with water and cook slowly with a little sugar and cinnamon until soft. Puree finely in a tower blender and chill. Peel pears, grate finely and freeze on a mold (or cup) lined with clear plastic wrap in the freezer. Puree the frozen pears with the cucumber puree and cucumber liqueur and possibly a little liqueur sugar in a food processor to a fine sorbet. Serve in small iced glasses and garnish with pear pieces.