In a small bowl, cover currants with hot water. Let sit and plump for 15 minutes. In a saucepan heat the chicken broth and butter to a boil. Stir in the couscous. Remove from the heat and let stand, covered, for 5 to 10 minutes. Meanwhile, make the dressing: whisk together the lemon juice, cinnamon and olive oil. When the couscous is done, transfer it to a bowl and break up the lumps with a fork. Drain currants and add to the couscous. Stir in the scallions, pistachios and parsley. Toss the couscous with the dressing and serve.