Generously salt & pepper the chicken breasts on both sides. Heat olive oil in a frying pan. Brown the chicken very well on both sides until there is a deep golden crust. Turn down the heat and allow to finish cooking until meat is white all the way through. Immediately chill in the fridge. (I'll do it the day before.)
After the chicken is cooled, cube and/or shred the chicken into bite-size pieces. In a large mixing bowl, combine the Miracle Whip, Mayo, Pecans, Grapes & Celery. Blend well. Fold in the chicken. Test for salt.
Best to make the salad the day before and allow it to sit for all the flavors to marry.
Serving suggestion: Pile it on a croissant or in a pita.