In a nonreactive bowl, stir together the yogurt, lemon juice, and chives; set aside until serving. This will have to be refrigerated if the wait is more than 1 hour. Heat the oil in a large skillet. Add the onions; cook until soft, about 5 minutes. Put the spinach in a strainer; press on it firmly to remove the excess liquid. Add the spinach to the skillet; cook 3 minutes more. Transfer the mixture to a large bowl. Add the bread crumbs, walnuts and thyme; then stir and toss with a fork to combine. Add the water or broth; stir until blended. Season with salt and pepper. Place the turkey breast slices in a single layer on your work surface. Sprinkle lightly with salt and pepper. Divide the spinach mixture evenly among the turkey slices, patting and spreading it over the top half of each slice. Starting from the filled end, roll up each slice pinwheel style to enclose the stuffing and make a log-shaped roll. Coat each with no-stick cooking spray. Prepare your grill. Grill the turkey rolls 4 to 6 inches from hot coals for about 15 minutes. Turn the rolls three or four times, until they are well browned and turkey is completely cooked. Arrange the rolls on a platter. They are also very good cold. Spoon some of the yogurt sauce over the tops and garnish with the parsley. Pass sauce at the table. Recipe from California Walnuts. Per serving: 376 calories, 16 grams fat, 37% calories from fat.