Heat olive oil in large pot over medium heat. Add leeks or onions and saute for 5 minutes, or until softened. Stir in the garlic, cook until fragrant, then add the greens and salt. Saute, stirring constantly until the greens begin to wilt. Add the water and cook, stirring frequently, until the greens are greatly reduced in volume and the water is evaporated, about 10 minutes. Add the chervil or tarragon and parsley. Cook for another minute and turn off the heat.