Cook bacon in a large pot over medium heat until crisp. Remove and set aside.
Brown pork shoulder in the rendered fat, 6–8 minutes, then remove and set aside.
Add onion to the pot and cook 4–5 minutes until softened. Add mushrooms and cook 5 more minutes.
Return pork and bacon to the pot. Add sauerkraut, cabbage, tomato paste, broth, bay leaves, juniper berries, and caraway.
Bring to a simmer, cover, and cook 1 hour, stirring occasionally.
Add kiełbasa and cook 20–30 more minutes, uncovered, until the stew has thickened.
Remove bay leaves, season with salt and pepper, and serve hot.