Can I freeze leftover chicken mousse?
Should be fine, although like many things that are frozen, the texture and consistency may suffer a bit.
It's a judgment call on your part whether or not this product degradation based on freezing is acceptable to your standards.
You can freeze a very small portion, then defrost. That should give you a pretty good idea.
Most definitely. I make double batches of this one around the holidays, and freeze them in small containers from which I can invert and serve once thawed and brought to room temperature.
By the way, @yockthethinker, neither texture nor consistency suffers a bit.