In a large pan, fry the onion on a medium heat with the olive oil until soft and caramelising. Add the garlic and mushrooms and fry until the mushrooms have softened.
Add a large pinch of salt. Scoop out 2-3 tbsp cooked mushrooms and set aside.
Add the coconut milk and stock, then simmer for 10 minutes.
Using a stick blender or food processor blitz until creamy.
To serve, toast the bread, spoon the soup into bowls and drizzle with truffle oil and a swirl of coconut yoghurt.
Top with the bread, reserved mushrooms, thyme and toasted walnuts.