Preheat a frying pan. Pour in vegetable oil. Put prepared onion in hot oil. Fry the onion until golden, over medium heat, stirring occasionally, for 2-3 minutes.
Put the mushrooms, simmer all together for 2-3 minutes.
Season with salt, pepper, add curry. Mix well.
Add sour cream.
Stir, simmer covered over the lowest heat for 5 minutes.