In large saucepan, place chicken breasts and cover with cold water by 1 inch. Add onion, celery leaves and Kosher salt. Bring to boil, reduce heat to low and simmer for 10 minutes, until chicken is no longer pink in the center. Remove from liquid and set aside. Discard liquid.

When cool enough to handle, cut chicken into bite-size pieces. In large bowl, mix together chicken, celery, apples, scallions, grapes and almonds. Use sharp knife to split pineapple into sixths from top to bottom. Slice core off each pineapple wedge and slice off fruit, leaving tufts of leaves in tact. Set aside half the fruit for other use or garnish. Cut the remaining fruit into chunks and add to chicken mixture. Set pineapple wedges on 6 plates.

In small bowl, whisk together mayonnaise, sour cream and lemon juice; blend well. Add dressing to chicken mixture and toss thoroughly. Add salt and pepper. Spoon mixture onto pineapple wedges and serve.