Quite an interesting interpretation. Normally food is about words. However, fruit (a food) is sometimes not about words. It can be about people’s character (the fruit of the Spirit). See the meanings of bananas, pineapples, and other fruit. So there are deviations. If there are deviations for fruit there may be deviations for vegetables as well.
The fact that the onions were held captive (treated like human beings) indicates that, in this case, they did represent people and not words or truth, or lies.
If the onions did represent people, the fact that they were chopped or minced, suggests that they went through a difficult time. They were probably minced or chopped by knives (critical or bad words). See the meaning of knives or swords. It speaks of critical words or insults when negative.
So it was bad words that caused them to be broken or negatively influenced. This negative influence led to captivity and then the bad turn, left, as you indicated. They should have been influenced by God’s words, the truth, then these negative circumstances could have been prevented.
So whatever incident or events caused this situation, It could have been prevented. Your interpretation makes sense if this was an emotional restoration dream, caused by the fear of the negative impact of the current recession and the fear of the food supply being interrupted or negatively impacted. So your interpretation does qualify as a legitimate interpretation
Well done! However, my interpretation does make sense as well. As you know, it all depends on what the trigger or the circumstances was.