First cut the onion into small pieces and sauté in a pan with the oil. When the onion pieces are golden, add the mushrooms and let them steep for a few minutes.
Then deglaze with a little water (approx. 1 dl) and add the vegetable stock and cashew butter. Stir well and bring to the boil. Any water or cashew butter can now be added until the desired consistency is achieved.
The sauce tastes great with spaghetti, potatoes or rice.
Of course, other mushrooms can also be used depending on the season.