Shred or dice cooked chicken. Add the mayonaise, Dijon, cumin, lime juice, salt and pepper; stir to incorporate. Mix in red onion, jalapeno and cilantro. Refrigerate for several hours to let flavors meld. Serve mounded in avocado halves.
Note: Chicken breasts may be cooked by first drying with a paper towel. Season well with salt and pepper (or Mexican spice mix) then placing in a flat microwavable dish. Cover loosely (I just place the splatter lid over.) Microwave high for about 5-10 minutes, testing at intervals for doneness. Do not over cook.