Polish croquettes with mushrooms and sauerkraut

Name: Polish croquettes with mushrooms and sauerkraut
Prep time: 10 min
Cook time: 1 h 20 min
Total time: 1 h 20 min
Yield: 4 portions
Ingredients: 330 g water; 230 g full cream milk; 2 eggs; 20 g grapeseed oil; 310 g plain flour; 1 pinch sea salt; 500 g sauerkraut; 1000 g water; 1 tbsp oil; 1 onion; 500 g button mushrooms; 1 ½ tsp sea salt; 1 - 1 ½ tsp ground black pepper; 120 g breadcrumbs; 2 tbsp butter