Peel the potatoes and cut into similarly sized pieces for even cooking.
In a large soup pot, boil the potatoes for 20 minutes in salted water.
Fry the bacon in a frying pan, until just crispy. Drain on kitchen paper.
Add the sauerkraut to the bacon fat and allow to warm through.
Warm milk in a small saucepan.
Drain, shake and dry the potatoes with kitchen towels before mashing with a potato masher or ricer. Working quickly, add the boiled milk and butter. Season to taste.
Mix the sauerkraut through the mashed potato. Crumble the bacon and finely chopped celery leaves over the dish, mix again, and serve hot.