Quote Originally Posted by maati
I'll give the full version of the second sentence:

И всего-то в этом сосуде намешено в нужных пропорциях.

Will that change anything?
I think I would use намешано.
I found that in a dictionary:
намешать - to add while mixing
намесить - to prepare by means of mixing (kneading)
That also makes me lean towards намешано.