Simmer onion, celery, parsley, bouillon, and butter for 45-60 min.
Let onion/celery mix cool.
Combine with eggs and sage and mix.
Place in large mixing bowl and add croutons gradually, to avoid adding so much that it becomes too dry. The mixture should still be wet and able to stick together.
cut a piece of parchment paper to fit the size of the pan, butter the paper, and place the paper butter-side-down on the dressing.