Preheat the oven to 300°F
Add diced onion and half of the butter to a cold, oven-safe pan. Bring it to medium heat, stirring occasionally. Sweat the onions til they are lightly caramelized. Add the garlic and stir another minute, until the raw garlic scent is gone.
Cut the sausage into bite size pieces. (I cut mine into half moon shapes,) Add the sausage to the pan. Cook for five minutes, until the sausage is browned.
Add seasoning at this point and stir to combine. Cook for an additional minute.
Add potatoes. Add sauerkraut, including liquid. Stir everything to combine.
Cut the remaining butter into four pieces and place on top. Cover the pan loosely with foil and place in the oven.
Cook for 2 ½ hours or until the potatoes are fork tender. At the 1 hour mark, take the pan out of the oven to stir.
Serve with your favorite mustard and enjoy!