Heat oil and butter in a large saucepan. Add onion, garlic and mushrooms. Saute until vegetables are soft, but not browned. Add thyme, nutmeg, green beans and chicken broth. Bring to a boil, then reduce heat and cook, covered for 8-10 minutes until beans are tender, but still bright green. Transfer to blender and puree. Add cashew cream and blend until incorporated. Season to taste with salt and pepper.