Peel the asparagus spears and cut them into pieces. Cook al dente in boiling salted water with a pinch of sugar and 1 tbsp. butter for 10 to 15 min. Remove and drain well. Set aside 250 ml of the cooking juices.
Brush potatoes under running water, do in about 25 min. Cool, peel and cut into slices. Layer in a greased gratin dish. Roll up selkkaree, spread evenly on potatoes with asparagus spears.
Preheat the stove to 200 °C. Sweat flour in 30 g butter. Add asparagus broth and wine. Simmer gently for 5 minutes. Mix in processed cheese, crème fraîche, season with pepper. Spread evenly over casserole. Bake sprinkled with grated cheese for 25 to half an hour.