Cooking Method:

1. Preheat your oven top 400 F (200 C)
2. Line a baking sheet with aluminum foil.
3. Place wire rack over lined baking sheet.
4. In a large bowl,place russet potatoes,then drizzle with vegetable oil and season with salt and black pepper.
5. Rub the oil and seasoning into their skins.
6. Place russet potatoes onto wire rack and bake in preheated oven until toothpick inserted in the center of potatoes comes out clean(for 1hour and 10 minutes).
7. Remove cooked potatoes from the oven<set aside and allow to cool.
8. Preheat  2 teaspoons of vegetable oil in a large nonstick pan.
9. Add sausages in a single layer and brown for 3-4 minutes per side.
10. Remove cooked sausages from the heat and pat dry with paper towel.
11. Add the sliced onions to the same pan.
12. Season with salt and black pepper.
13. Allow the onions to caramelize to a deep golden-brown (for about 20-25 minutes) over a medium-low heat, stirring frequently.
14. Chop cooled sausages into a bit size.
15. Add the chopped bratwurst bits into the pan with caramelized onions.
16. Stir well to combine and add lager beer.
17. Allow the beer to reduce for a moment and become glossy and just slightly thickened.
18. Turn off the heat and season(if necessary) with salt and black pepper.
19. Set onion and sausage mixture aside,keeping warm.
20. Cut cooled potatoes in half lengthwise, and carefully scoop out most of the flesh leaving about 1/2 inch(1.25 cm) border of potato, reserving the flesh for another use.
21. Brush inside of potatoes with melted butter and sprinkle with salt and black pepper.
22. Return potatoes to the wire rack, flesh-side up.
23. Place under the broiler and brown for a few minutes, and once inside is slightly browned, flip the potato and crisp the skins for a couple of moments.
24. Fill each potato with sausage-onion mixture.
25. Sprinkle with cheese mixture.
26. Return to the heat and broil until cheese is melted.
27. Top with sauerkraut and serve potatoes stuffed with bratwurst sausage and sauerkraut immediately.