Melt butter in a large pot over medium heat. Add onion and celery, cooking 5 minutes until softened.
Add chicken and cook 5–6 minutes, until lightly browned on the outside.
Pour in broth and poultry seasoning. Simmer 20 minutes, until chicken is tender.
Whisk xanthan gum into the broth to thicken slightly.
For the dumplings, beat egg whites with cream of tartar until stiff peaks form. In a separate bowl, beat egg yolks with softened cream cheese until smooth, then gently fold into the whites.
Drop spoonfuls of the dumpling batter onto the surface of the simmering broth. Cover and simmer 8–10 minutes, until dumplings are set and puffed.
Season with salt and pepper and serve hot.