Take package of cauliflower rice out of the freezer and measure out 1 cup frozen cauliflower rice. Let it thaw on the counter while you start the soup.

Heat 2 tsp. olive oil in a non-stick frying pan and brown the turkey, breaking it apart with the turner as it cooks. Season with salt and fresh ground black pepper. Put browned turkey into a large soup pot.

(If you're making the soup with leftover turkey I'd use about 3 cups of diced turkey; don't add that to the soup pot until later.)

Add another 2 teaspoons olive oil to the frying pan and saute the onions about 4 minutes; then add the garlic, thyme, poultry seasoning, and Spike Seasoning (affiliate link) and cook about 2 minutes more. Put the onion mixture into the soup pot.

I made mushroom stock with water and the imported mushroom base cubes you see in the photo, but those are hard to find and Better Than Bouillon Mushroom Base (affiliate link) is also great.

Add vegetable stock (or canned vegetable broth) and mushroom stock to the soup pot with the turkey, onions, celery, and spices. Turn on stove under the soup pot to medium and let it start to cook, turning it to a low simmer as soon as it start to bubble.

Wash the mushrooms if needed and then cut into thick slices and then cut slices in half. Add mushrooms to the soup pot.

Simmer soup until the mushrooms are done and the mixture is starting to smell like soup, at least 20 minutes after you add the mushrooms.

(If you're using leftover turkey I'd add that after the 20 minutes is up.)

Then add cauliflower rice to the soup pot and simmer about 10 minutes more.

Coarsely chop the spinach. When you think the cauliflower rice is close to being cooked, add chopped spinach to the soup pot and cook 10-15 minutes more.

Add 2 T fresh-squeezed lemon juice if desired (optional), cooking a few minutes more if you add the lemon juice.

Serve hot, with grated Parmesan cheese to add at the table if desired.