Dear Mr. Grammaton Cleric, if feel really terrible that I have disappointed you. I am looking forward to discuss this Stroganoff fiasco with you, maybe at a nice dinner? I buy some 600 g / 1.2 lb scotch fillet steak, 2 tbsp vegetable oil, 1 large onion (or 2 small onions), 300 g / 10 oz mushrooms, 40 g / 3 tbsp butter, 2 tbsp flour, 2 cups / 500 ml beef broth, 1 tbsp Dijon mustard, 150 ml / 2/3 cup sour cream and Salt and pepper.