Prepare as for Kalbsschnitzel, follow preceding recipe and while the Schnitzels are cooking cut peppers in half and remove stems and seeds. Cut crosswise in thin half rings. Peel onion, cut in half lengthwise, then into thin slices. Fry pepper half rings and onion half rings in a small frying pan until soft. Just after adding the sour cream add fried peppers and onions to sauce. Let simmer 1 hour. Place Schnitzels on prewarmed plates. Pour sauce with mushrooms, peppers and onions on Schnitzels and garnish with parsley and lemon wedges.