In the soup itself, I only used 2-3 tablespoons of butter (not 6!)
I didn't use celery.
For the chicken, I used 1.5 pounds boneless, skinless chicken thighs, cut into 2-inch pieces. I dropped it raw into the soup and let it cook in the soup for ~15 minutes while preparing the dumplings. (This could possibly use more chicken; it was a bit scant on chicken.)
In the dumplings, I think I used about 3 tablespoons of melted butter. I ended up adding like another 4 tablespoons of milk because it was too dry.
Before putting in the dumplings, I put a bag of frozen peas in the soup.
Then I added the dumplings just using a regular kitchen spoon. They still ended up quite big!
I cooked the dumplings for 20 minutes