Preheat your oven to 400°F (200°C) and prepare a baking sheet with parchment paper.

Wash and slice the russet potatoes into even rounds, about ¼ inch thick. Spread them on the baking sheet and roast for 30–40 minutes, flipping halfway.

While the potatoes roast, heat a skillet over medium and cook the smoked sausage until browned, about 8–10 minutes.

In the same skillet, sauté sliced onions over medium heat until caramelized, about 5–7 minutes. Then add German lager and simmer for 3–4 minutes.

Layer the potato stacks: start with a potato slice, add sauerkraut, sausage, and beer-braised onions. Repeat until all ingredients are used.

Serve warm on a platter or in appetizer cups for sharing.