Place the porcini mushrooms in a small dish, add boiling water, leave to soak. *Note: Strain the soaking liquid before cooking.
Heat the butter in a heavy-bottomed pan over medium heat.
Toss in the onions, saute them until softened and browned.
Add the garlic and cook until soft.
Add the carrots, mushrooms and celery stalks and let it cook slowly until they soften.
Place the vegetable mixture in the bottom of the crockpot.
Place the chicken on top of the vegetables, bay leaf, thyme and pour in low sodium chicken broth.
Cover and cook on low for 6 hours or high heat for 3-4 hours.
Rinse the wild rice thoroughly and pour it into the slow cooker about halfway through the cooking process.Note: If you are worried about the rice getting too mushy, you can use pre-cooked rice and add it to the slow cooker about 10 minutes before serving. About 20-30 minutes before the cooking is done, remove cooked chicken from the slow cooker and shred into small pieces. Pour in the heavy cream. The heavy cream will make the soup thicker and less liquid.
Season with salt/pepper.