Season the diced beef fillet with salt and pepper and saute well in hot oil. Add the diced pepper and saute.
Remove the meat and peppers from the pan and put to one side. Deglaze the pan and add goulash sauce. Boil for a few minutes.
Return the meat and peppers to the sauce and stir in the finely chopped chocolate and cold butter.
To serve the goulash in a deep dish with sour cream, rest of the lemon zest, garlic, marjoram and caraway with celeriac puree. Serve fresh with bread on the side.