Heat olive oil in a large pot over medium heat.
Add chopped onion and sauté for 3-4 minutes until softened.
Stir in minced garlic and sliced mushrooms, cooking for another 2 minutes until fragrant.
Pour in the broth and bring to a simmer.
Add the wild rice and thyme, then cover and cook for 20 minutes.
Stir in the mixed greens, salt, and pepper, then simmer for another 10 minutes until the greens are tender.
If using optional proteins like cooked chicken, sausage, or white beans, add them now and heat through.
Taste and adjust seasoning as needed.
Serve hot with crusty bread on the side.