Sous Vide chicken for reheating
You'll want to do some research on sous vide. That way you can use the correct process and terminology.  Cook and chill is common practice in sous vide cooking.  Vacuum is not necessarily required.  To make a chicken nugget, you'll want to bread the chicken after the sous vide step.  For example, you could cook the chicken pieces, allow to cool a bit, blot dry, coat, then brown/crisp the coating.  Your best methods would be to deep fry, pan fry, or heat in oven. If using right away, this will allow you to achieve perfectly cooked chicken with a crust that you like.  You could sous vide a degree or two lower, with the realization that the browning step will finish the cooking. The challenge is to avoid overcooking the chicken when browning the coating, especially if cooking from frozen.  Since chicken nuggets cook relatively quickly, in the end, sous vide may not be the best tool for the job here, as you could easily achieve the same result, more quickly, using traditional methods.