Combine oil, onion and garlic in a large saucepan and heat over medium until onions are translucent. Add sprinkling of salt and pepper.
Add finely chopped portabello mushroom (make sure to scrape out the black underside of the mushroom). Continue to heat over medium until mushrooms are softened (approx 7-10min).
Add vegetable broth, bring to a low boil and then simmer for approx. 10min.
Add soup mixture to blender (we use the Blendtec) with cilantro and blend until smooth.
Stir in cayenne pepper and chilli powder to taste.