Heat 1 tablespoon olive oil and 1 tablespoon butter in a 5-quart enameled Dutch oven or heavy soup pot over medium-high heat. Season cubed chicken breasts with 1/2 tsp salt and 1/4 tsp black pepper. Add chicken to the hot pot in a single layer and sear without moving for 3 minutes until lightly browned on the bottom, then stir and cook for 2 more minutes until nearly cooked through. Transfer seared chicken to a clean plate and set aside.

Reduce heat to medium. Melt the remaining 1 tablespoon of butter in the same pot. Add the diced yellow onion, sliced carrots, and diced celery. Sauté for 5 to 6 minutes, stirring frequently with a wooden spoon, scraping up any caramelized chicken bits from the bottom of the pot until the vegetables soften and sweeten.

Stir in the minced garlic, dried Italian seasoning, and chopped fresh thyme. Cook for 60 seconds until fragrant.

Sprinkle 2 tablespoons of all-purpose flour evenly over the sautéed vegetables. Stir constantly for 1 to 2 minutes to cook out the raw flour taste, coating the vegetables in a light paste.

Slowly pour in 4 cups of low-sodium poultry bone broth in a steady stream, whisking or stirring continuously to dissolve the flour evenly and prevent lumps. Bring the soup to a gentle boil over medium-high heat, stirring as it thickens into a silky broth.

Return the seared chicken and any resting juices back into the pot. Reduce heat to medium-low, cover partially with the lid, and simmer gently for 8 minutes to tenderize the chicken and blend the flavors.

Uncover the pot and gently slide in the 10 oz of fresh refrigerated three-cheese tortellini. Stir gently to submerge the pasta and simmer uncovered over medium-low heat for 3 to 4 minutes, just until the tortellini float to the top and become pillowy and tender. Do not overcook.

Reduce heat to low. Stir in the 3/4 cup of heavy cream, 1 teaspoon of fresh lemon juice, and a pinch of ground nutmeg. Simmer for 1 minute until warmed through.

Add the 3 cups of fresh baby spinach in two batches. Stir gently for 60 to 90 seconds until the leaves just wilt and turn vibrant bright green.

Remove the pot from heat. Fold in the 1/2 cup of grated microbial parmesan cheese, stirring gently until it melts seamlessly into the broth, creating a velvety, luxurious texture.

Taste the broth and adjust salt and pepper if needed. Ladle the hot soup into warmed shallow ceramic bowls, ensuring a generous balance of tender chicken, cheesy tortellini, and vibrant spinach in every bowl.

Garnish each bowl with fresh chopped Italian parsley, an extra pinch of shaved parmesan, and freshly cracked black pepper. Serve immediately with warm toasted garlic sourdough.