Heat 1 tablespoon olive oil in a large Dutch oven/soup pot oven over medium high heat. Add chicken and sear on each side, about 2 minutes per side. Remove chicken.
Add 2 tablespoons butter/oil to the now empty pot and heat over medium high heat. Add onions and mushrooms and cook, stirring occasionally for 6 minutes. Add carrots and cook until tender – about 4 minutes. Add the garlic and thyme and cook 30 seconds. Add remaining spices, corn, chicken stock and chicken back to the pan.
Bring to a boil; cover and reduce to a gentle simmer. Simmer 10 minutes, remove chicken and let rest 2 minutes then shred.
Meanwhile, bring soup back to a boil. Add tortellini and boil 1-2 minutes or until tender.
Remove from heat and stir in spinach, lemon juice and chicken.
Taste and add additional lemon, salt, pepper to taste. Remove bay leaves.
Garnish with freshly grated Parmesan cheese and lemon zest (optional)
TO MAKE IN THE SLOW COOKER
Sear chicken as instructed above and add uncut chicken to the bottom of a slow cooker, followed by all of the remaining ingredients EXCEPT for the tortellini, spinach, lemon juice and Parmesan. Cover and cook on low heat 6 - 7 hours or on high for 3-4 hours.
When ready to serve, remove chicken to a cutting board and let rest for 10 minutes. Meanwhile, add tortellini to the slow cooker (turn to high heat if on low). After 10 minutes, shred chicken and add back to slow cooker along with spinach and lemon juice. Tortellini should be about cooked by this time, approximately 15 minutes total. When tortellini is completely cooked and spinach wilted, taste and add additional lemon, salt, pepper to taste. Remove bay leaves. Garnish with freshly grated Parmesan cheese and lemon zest (optional)