Closely adapted from George Lang.
Slowly cook the bacon in a medium-large Dutch oven, until the fat is rendered and the bacon is crispy. Remove the bacon and set aside.
Add the onion with a pinch of salt and cook until softened. Stir in the paprika with the half cup water. Bring to a boil and let simmer for 5 minutes.
Add the beef, a hefty pinch of salt, black pepper, caraway seeds, marjoram, and 1/2 cup of the wine and return to a simmer. Cover the pot and let simmer, gently, for 30 minutes.
Add the pork tenderloin with the remaining 1/2 cup of wine and a pinch of salt. Bring back to a simmer and cover again. Let simmer gently for 2 1/2 hours. This stage could also be done in a 300 F oven if it is easier.
About 25 minutes before serving, prepare the potatoes.
About 15 minutes before serving, while the potatoes are cooking, heat the bacon grease in a skillet. Add the mushrooms with a pinch of salt. Cook until all of their water has released and they are starting to brown.
Add the mushrooms to the stew and crumble the bacon in it as well. Stir to incorporate.
Right before serving, whisk the flour into the sour cream, and then slowly whisk the hot stew liquid into the sour cream. When the sour cream is hot, then add it all into the stew and stir to incorporate. Bring it back to a simmer and then turn off the heat. Taste for more salt.
Serve over the boiled potatoes.
According to Lang, both the Hungarians and Romanians lay claim to this stew, so I just gave it to both!