In a large soup pot, heat 2 teaspoons of olive oil over medium heat. Add the diced onion and chopped celery, and sauté until they are soft, about 5 minutes.
Add the lean ground turkey to the pot, breaking it apart with your wooden spoon. Season with salt, pepper, and the minced garlic. Cook until the turkey is browned and cooked through, about 7-8 minutes.
Stir in the dried thyme, poultry seasoning, and Spike seasoning. Let these spices toast for about a minute to release their flavors.
Add the vegetable stock and mushroom stock to the pot. Bring the mixture to a simmer, scraping any browned bits from the bottom of the pot for added flavor.
Add the sliced brown Cremini mushrooms to the pot. Let them simmer in the soup for about 10 minutes, until they are tender and have released their juices.
Add the frozen cauliflower rice and chopped spinach to the pot. Stir well and cook for an additional 5 minutes until the spinach is wilted and the cauliflower rice is heated through.
Remove the pot from heat and stir in the fresh squeezed lemon juice. Taste and adjust seasoning if needed.
Ladle the soup into bowls and, if desired, top with freshly grated Parmesan cheese. Enjoy your nourishing bowl of Ground Turkey Soup with Mushrooms and Spinach!