In a large skillet, heat the olive oil and add the chicken. Season with ½ teaspoon salt and ¼ teaspoon pepper. Cook until the chicken is cooked through, for about 5 minutes. Transfer to a plate and set aside.
Heat the butter in a large heavy pot and add the mushrooms, leek, bell pepper, and carrots. Cook, stirring, until softened, for about 5 minutes. Add ⅛ teaspoon salt, ⅛ teaspoon pepper, and garlic, and cook,stirring, for 1-2 minutes more.
Add the white wine and thyme, and cook for a minute more. Now add the flour and stir to coat the veggies. Cook for 1 minute more. Add the chicken broth, water, and simmer on a low heat for 15 minutes. Add the spinach and cooked chicken and cook for another 15 minutes. Stir in the heavy cream and simmer for 3-5 minutes more.
Top with the Parmesan cheese and croutons, if desired, and serve. Enjoy!