Heat oil and butter in a large heavy bottomed pot or dutch oven over medium/high heat.
Add the onion and cook until softened and golden, about 8 minutes.
Add garlic, mushrooms, season with salt, and cook until mushrooms have released their water and are beginning to brown, another 8 minutes.
Stir in flour and cook 2-3 minutes. Slowly pour in wine and broth, continually stirring.
Mix in base and then add celery, carrots, and potatoes.
Bring to a boil and reduce to a simmer. Add herbs, onion & garlic powder. Cover and simmer 30-40 minutes until vegetables are tender, stirring occasionally.
Add salt, pepper and turkey. Stir in cream, if using. Simmer until heated through. Ladle into bowls and serve.
Servings 8
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.