In this case I just swapped in celery root + some garlic for the onion, and it was delicious! This is probably unsurprising given that the stuffing recipe consists of: onion/celery root, sage, basil, nutmeg, breadcrumbs, Swiss cheese, and cream.

For pumpkin #2, I put in the other half of the celery root AND the onion. Also delicious.

I think the only thing I'd change for next year is to use one of these blue pumpkins for the dish, because the pumpkin flesh in this one is amazing!