Peel and dice the onion. Clean and quarter the mushrooms.
Melt the clarified butter in a pan, add the onions and sweat until translucent. Add the mushrooms and fry them. Dust with flour, stir and deglaze with the milk. Season with vegetable stock and paprika powder. Let the sauce boil down to the desired consistency. Season to taste with salt, pepper, paprika powder and chopped parsley.
The sauce goes well with spaetzle and is ready in the time the spaetzle need to cook.