This is so delicious (and it's really Swiss, not German, but there wasn't a Swiss cuisine so I selected the closest possible match). This version is different than other recipes of the same title in that it uses wine and cream that produces a delectable creamy sauce. Traditionally, the recipe calls for veal and veal kidney, but pork loin and chicken can be used in place of veal. It's usually served with Swiss Rosti (hash brown or pan-fried potatoes) and paired with a Swiss white wine or Pinot grigio.
Melt 1 tablespoon clarified butter (or oil) over high heat and quickly brown meat strips in it until no longer pink. Remove from pan and keep warm.
Add 1 more tablespoon of clarified butter to pan, if necessary, and stir in shallots and cook for 2 minutes. Add mushrooms to pan and cook until soft and brown. Sprinkle mushrooms with flour and stir. Cook for 1 minute.
While stirring, slowly add the wine and broth to the mixture. Bring to a boil and cook until sauce is reduced by half.
Stir in lemon zest, cream, salt and pepper to taste. Add the browned meat back to the pan to warm, but do not cook the sauce any longer.