Step 1

Preheat oven to 400 degrees F.

Step 2

Heat 2 teaspoons oil in a large skillet over medium heat. Add onion and cook, stirring, until beginning to brown, about 5 minutes. Stir in caraway (or fennel) seeds and cook until fragrant, about 30 seconds. Add apple and wine; increase heat to medium-high and cook, stirring, until most of the wine has evaporated, about 5 minutes. Stir in sausage, sauerkraut, vinegar, mustard and pepper. Transfer to a 9-by-13-inch (or similar 3-quart) baking dish.

Step 3

Toss potato slices with the remaining 2 teaspoons oil, butter and salt in a bowl until coated. Cover the sauerkraut mixture with tightly overlapping potato slices.

Step 4

Bake the casserole until the potato edges start to get crispy, 50 minutes to 1 hour. Cool for 10 minutes before serving.