Use 1 1/2 lb. peameal bacon roast or a smoked pork loin roast.
Use 4 potatoes, preferably Yukon Gold because they are firmer and don't fall apart as easily.
Use one 28 oz. can Sauerkraut, drained.
Liquid - 1 cup of either apple juice, orange juice, or water.
Instructions:
Put Peameal Bacon Roast and drained Sauerkraut in slow cooker (crock pot).
Add peeled potato quarters to the slow cooker, making sure the potatoes are pushed well to the bottom. Potatoes need to be in liquid to cook properly. Even though there is not enough liquid in the cooker to start, there will be once it cooks for a few hours.
Pour in about 1 cup of apple juice, orange juice, or water.
Cook, covered on low to medium, for about 6 hours. Check your slow cooker instructions for approx. times.
Remove potatoes, meat, and sauerkraut. Keep warm.
Put cooking liquid into saucepan, bring to boil, and thicken with 1 - 2 tbsp. cornstarch dissolved in some cold water. Use as a sauce for the meal.
Instead of using kassler, use a peameal bacon roast. The resulting flavour is so similar. 
Ingredients:
