1. In a large skillet, melt butter over medium-low heat. Add onion. Cook, covered, for 13 to 15 minutes or until tender, stirring occasionally. Uncover; cook and stir over medium-high heat for 3 to 5 minutes more or until golden.
2. In a large bowl, combine onion, chicken, walnuts, and green onion. Add mayonnaise, cilantro, and lime juice; toss to coat. If desired, season to taste with salt and pepper.
3. Place about 1/2 cup chicken salad on each of five bread slices. Top each with two slices tomato and some of the spinach. Top sandwiches with the remaining bread slices. If desired, secure each sandwich with a skewer and garnish with an olive. Makes 5 servings.
Shredded Chicken Master Recipe:Place 4-1/2 to 5 pounds chicken thighs, skinned, in a 4- to 5-quart slow cooker. For bouquet garni, cut an 8-inch square from a double thickness of 100 percent cotton cheesecloth. Place 4 thyme sprigs, 4 parsley stems, 2 bay leaves, 2 cloves garlic, halved and 1/2 teaspoon whole black peppercorns in the center of the cheesecloth. Bring up corners of the cheesecloth and tie with 100 percent cotton kitchen string. Add bouquet garni to slow cooker. Pour 1, 32-ounce box chicken broth over all. Cover and cook on low-heat setting for 7 to 8 hours or on high-heat setting for 3-1/2 to 4 hours. Remove bouquet garni and discard.Using a slotted spoon, transfer chicken to a large bowl. When chicken is cool enough to handle, remove meat from bones. Using two forks, shred meat. Add enough of the cooking juices to moisten meat. Strain and reserve cooking juices to use for chicken stock. Place 2-cup portions of chicken and chicken stock in separate airtight containers and refrigerate for up to 3 days or freeze for up to 3 months. Makes 6 cups.