"The Organizer Man" on Facebook had a great video demonstrating how to make Cream of Chicken Soup Powder to keep in canning jars.
He used a rolled up piece of plain paper as his funnel into a full size canning jar since he does not can and does not have a canning funnel.
I think this is far less than a canning jar will hold so feel free to multiply this basic unit recipe to fit your jar.
In a bowl, add 2 cups all purpose flour, 2 and 1/2 cups of non-fat dried milk powder, 1/4 cup of chicken bullion granules
(I like Herb Ox since it is low sodium), and 2 tablespoons of dried onion flakes or powder.
Mix dry ingredients together very well.
Pour into your canning jar. and put the lid on very tightly. Store in a cool, dry place.
When you want to make soup or the base/sauce for a casserole, combine 1/2 cup of soup mix with 1/4 cup of milk.
You could add other things at this point like mushrooms, garlic, pepper, etc.