1. Place a medium saucepan over medium heat and add the butter or olive oil. Add the onion and fry until fragrant and translucent but not browned,about 3 minutes. Add the cauliflower and stock and bring to a simmer. Simmer for about 10 minutes,until the cauliflower has softened,then transfer to a blender and blend to a smooth puree. Add the yoghurt,season with salt to taste and serve. 

Adam's tip: A high-speed blender is a very useful tool in the kitchen,particularly for soups. It will give you a silkier texture than normal blenders will,and you won't need to bother with a strainer.

Also try:Adam Liaw's salted honey and tahini shortbread