First, add celery, carrots, onions, garlic cloves, oregano, pepper, baby Bella mushrooms, shiitake mushrooms, Parmesan rind, and chicken stalk to the slow cooker and mix.
Next, add fresh thyme to the top (so it is easy to fish out/see video above).
Now, cover and cook on low for 8 hours (or as long as you are at work).
Next, take out the thyme bundle and add spinach and tortellini for 15 minutes.
Finally, add a teaspoon of salt and enjoy!