Preheat the oven to 400 degrees.

In a pot of boiling salted water cook the potatoes until tender. Drain well.

Meanwhile, combine sauerkraut and scallion; place in a casserole dish.

Lay the sausage over the sauerkraut.

Drain potatoes; mash with milk, butter, salt and pepper.

Spread potatoes over sausage; sprinkle with Parmesan cheese.

Bake in the oven for 25 to 30 minutes or till lightly browned.