Combine the chicken broth and dried garlic in the basin of a medium slow cooker.
Add the cauliflower florets, cover, and cook on Low for 4-5 hours or on High for 2-3 hours, until the cauliflower is very tender.
Carefully transfer the cauliflower and any remaining cooking liquid to a large mixing bowl. Use an immersion blender or a hand mixer to blend until smooth and creamy.
Stir in the softened butter, sour cream, salt, and pepper until well combined.
Taste and adjust the seasoning as needed.
Garnish with fresh parsley and serve immediately.