Hello, janisoga,

I like to think that with my big collection of cookbooks, that I can find many recipes--but I have, quite flatly, struck out on this one. It's not in balls--and I guess it's more of a dip, but this is the closest I could find to what you are inquiring about (and it's from the internet, not my cookbooks:

Here is a link that might be useful: Appetizer with soup mix and bread and cheese

The onion soup mix didn't click, but are you thinking of something like these spinach balls? They're made with stuffing mix and cheese. Not sure if this is the same recipe my family used, but it's close:
http://allrecipes.com//Recipe/spinach-balls/Detail.aspx

My family used to make them all the time many years ago and they've had a revival recently. I also saw them served at a party recently with a mustard sauce for dipping and they were a huge hit!

Try googling "Bake cheese balls". there were too many hits to sort.