Question:
I work in a Kitchen where we make a crumble for a cake can the non Jew who mixed the dough take the challah from it as it is taken without a bracha?
If yes what about if it is dough that needs a bracha?
Answer:
A gentile is not a valid shaliach, and cannot take off challah, even if the amount is only required m’drabonon. Challah should be taken off again.
Best wishes
Sources:
Mishnayos Terumos 1-1, and challah is like teruma, Mishpitei Eretz 4-3.