Preheat oven to 325 degrees.
Add walnuts to a small pan, toast in the oven for 10 minutes. Allow to cool.
Preheat oven to 375 degrees.
Add chicken breast to a small casserole dish and sprinkle with paprika. Bake chicken approximately 15 to 20 minutes or until juices run clear. Allow to cool. Remove skin and bones, cut into bite-size pieces.
In a medium bowl combine bok choy, celery or bok choy, walnuts, red grapes, black pepper, and salt. Add chicken pieces and mayo, toss to coat.
Lightly toast bread, add chicken salad to two pieces of toast, top with the other two pieces of toast. Cut the two sandwiches in half and serve.