The parsley and watercress turn this broth a vibrant green.
In a medium saucepan, combine 1 1/2 cups parsley, 1 cup watercress, shallots, 1 1/2 cups water, and 1 teaspoon salt. Bring to a boil. Reduce heat, cover, and simmer for 30 minutes. Strain; reserve liquid. Set aside.
Season scallops on both sides with salt and pepper. Heat 1/2 teaspoon oil and 1/2 teaspoon butter in a large skillet over medium heat. Cook half the scallops until golden brown, 5 minutes. Turn, and cook for 3 more minutes. Keep warm; repeat process.
Return broth to a boil. In a blender, combine remaining parsley and watercress with hot broth. Cover blender with a towel to absorb any splashes, hold top firmly in place, and puree. Strain, and adjust seasonings. Pour broth into serving dish; place scallops on top.