What can I use to flavor savory chicken stuffing instead of onion? I made the mistake of thinking I had more onions than I did (those orange bags filled with old onion skins look fuller than they are), and now I don't have any onions left for my savory dressing. Can I use onion soup mix (with those little dehydrated onion flakes), or would this goop up when I mix in melted margerine? What about onion powder for the flavor? I have some mushrooms. Could I combine this with onion powder?

My concerns are that the chicken will be lacking in onion flavor, that the drippings might be bland, or powder substituted in for moist onion might dry out the stuffing.

The recipe* calls for Breadcrumbs, summer savory, margarine/butter and diced onion. When it's put into the chicken carcass and cooked it absorbs the chicken's essence. It makes a nice stuffing, but the onion tends to be a key part of the flavor.

Also, I don't have shallots or any other reasonable onion alternative.  

*by recipe, I mean "mix them together until it looks/feels right".

Update: I ended up using the onion soup mix and a bit of celery I had left over. It started out goopy when I first mixed it togther, but the end result was flavorful and moist.
I use dehydrated onion soup mixture as a substitute to many preparations calling for onions. I have never stuffed chicken with it, but I would do it without any doubt. 

The trick is to get to the appropriate moisture and salt point. I use both water and some other sweet liquid (7up, sprite, coke...) to rehydrate and reduce the slight salty taste of the dehydrated onion. 

For your case, besides the sweetening, the soft drink will as well add some carbonic which may also help in aerating a bit the stuffing.