Thanks Helen! I think "kit" could work, when the rice is included. But when its just the sauce I'm still not sure which word to use. So far I'm leaning towards "sauce for..." or even "cooking sauce for..."
As for "creamy" or "brothy", the problem here is that there is also an "arroz caldoso", which I have translated as "brothy rice". "Arroz meloso" is not the same, as it's inbetween a dry rice and a brothy rice (see
https://www.proz.com/kudoz/spanish-to-english/cooking-culina... I'm glad you like my question! I love this topic too : )