In your large pot, heat the olive oil and butter over medium heat. Once melted, add the chopped onion, sliced mushrooms, and carrots. Sauté for about 5-7 minutes, or until the vegetables begin to soften. Add the minced garlic and cook for an additional minute until fragrant.
If using raw chicken thighs, add them to the pot now. Sprinkle in the chicken bouillon, dried parsley, salt, thyme, oregano, cumin, pepper, red pepper flakes, and bay leaves. Stir everything together to coat the chicken and vegetables in the spices.
Pour in the low sodium chicken broth, ensuring the chicken is submerged. If you’re using shredded rotisserie chicken, wait until later to add it. Bring the mixture to a boil, then reduce the heat to low and let it simmer for 20 minutes.
If you used raw chicken, after 20 minutes, remove the chicken thighs from the pot and shred them using two forks. Return the shredded chicken back to the pot. If using rotisserie chicken, simply add it to the pot at this stage.
Stir in the uncooked cheese tortellini and sweet corn. Let it cook for another 5-7 minutes, or until the tortellini are cooked through.
Add the fresh spinach and lemon juice to the pot. Stir gently until the spinach has wilted. Taste and adjust seasoning with more lemon juice, salt, or pepper if needed.
Remove the bay leaves before serving. Ladle the Lemon Chicken Tortellini Soup into bowls and garnish with freshly grated Parmesan cheese and lemon zest if desired. Enjoy the comforting warmth and zesty flavors!