
Prepare a liquid base for the sauce. In a deep bowl, combine water and flour, stir until smooth.

Place the champignons in a preheated frying pan with sunflower oil and fry over high heat for 10 minutes. Add chopped onion and crushed garlic. Reduce heat to medium and fry for 5-7 minutes, stirring occasionally. Add the chicken fillet to the mushrooms and onions. Reduce heat to minimum.

Pour the flour mixture into the pan with the mushrooms and chicken. Add sour cream and butter. Season with salt and pepper. Mix thoroughly. Cover and simmer for 10 minutes.