Prepare Your Ingredients
Shred the rotisserie chicken into bite-sized pieces, removing any skin or bones. Set aside.
Dice the onion, chop the celery, slice the mushrooms, and crush and mince the garlic. Have all ingredients ready before cooking.
Build Your Flavor Base
Heat a large soup pot or Dutch oven over medium heat. Add olive oil or butter.
Add diced onion and chopped celery. Cook for 5 minutes, stirring occasionally, until onions are soft and translucent.
Add the Mushrooms
Add sliced mushrooms to the pot. Cook for 5-7 minutes, stirring frequently, until mushrooms are golden brown and caramelized.
Infuse with Aromatics
Add crushed garlic and fresh thyme leaves. Stir constantly for 1-2 minutes until fragrant. Be careful not to burn the garlic.
Create the Creamy Broth
Pour in chicken broth, scraping the bottom of the pot to release any flavorful bits.
Add heavy cream and stir until well combined. Increase heat slightly to bring to a gentle simmer. Let simmer for 5 minutes.
Add Chicken and Greens
Lower heat to medium. Add shredded rotisserie chicken and stir gently.
Add chopped spinach in handfuls, stirring after each addition. Simmer for 5 minutes until spinach is wilted and chicken is heated through.
Season and Perfect
Taste and season with salt and black pepper as needed. Add chili flakes if desired. Adjust seasoning to taste.
Let soup rest for 5 minutes before serving.