Sauté the Veggies: Melt the butter or oil in a large stockpot over medium-high heat. Add the diced onion and cook for about 4 minutes, stirring occasionally. Add the carrots, celery, and garlic, and sauté for another 3 minutes. Stir in the flour and cook for 1 minute, stirring constantly to avoid burning.
2 tablespoons butter or olive oil, 1 small white or yellow onion, 2 medium carrots, 2 celery stalks, 6 garlic cloves, ¼ cup all-purpose flour
Build the Base: Slowly pour in the chicken broth while stirring to make sure the flour dissolves smoothly. Add in the chicken breasts, mushrooms, wild rice, rosemary, and bay leaves. Give everything a good stir.
6 cups chicken broth, 1 pound boneless, 8 ounces baby bella mushrooms, 1 cup uncooked wild rice, 1 tablespoon fresh rosemary, 2 bay leaves
Simmer the Soup: Bring the soup to a gentle boil, then reduce the heat to medium-low. Cover and simmer for 40 to 45 minutes, stirring every 5 to 7 minutes to keep anything from sticking to the bottom. The rice should be tender by the end.
Shred the Chicken: Use tongs to carefully remove the chicken breasts. Shred the meat with two forks (or chop it into bite-sized pieces), then stir it back into the pot.
Creamy Finish: Add the milk and chopped spinach to the soup. Stir until the spinach wilts and everything is heated through.
2 cups milk, 2 cups baby spinach
Taste Test and Serve: Remove the bay leaves. Season the soup with salt and pepper to your taste. Ladle into bowls and serve warm.
Salt and black pepper