Add the cauliflower florets, raw cashews, diced onion, minced garlic, vegetable broth, dried thyme, salt, and black pepper to the slow cooker.
Stir the ingredients to combine them evenly.
Cover and cook on low for 6 hours until the cauliflower is very soft.
Turn off the slow cooker and let the soup cool for 10 minutes.
Use an immersion blender to puree the soup until it reaches a smooth consistency.
Stir in the lemon juice.
Ladle the soup into bowls and sprinkle with chopped fresh chives before serving.