Add the celery, carrots, onion and thyme to the fat left in the pan along with another tablespoon of butter.
Stir occasionally for about 6-8 minutes until softened.
Stir in the garlic and cook for another minute.
Stir in mushroom powder.
Sprinkle the flour over the vegetables and cook, stirring, until evenly coated and lightly browned, about 3 minutes.
Add the wild rice to the pan and gradually stir in the stock.
Stir in the baking soda and add the parmesan rind.
Bring to a boil and then reduce the heat.
Nestle in the chicken, then simmer uncovered over moderately low heat, stirring occasionally, until the chicken is cooked through and the vegetables are tender, about 30 minutes.