Bake the Kassler in the roasting tube for approx. 1 hour at 200C in the oven.
Chop the meat cold and layer it in a pan in layers. Pour the roast stock from the roasting tube over it.
Thaw the rösties and mix with the other ingredients (except the cheese). Spread the mixture on the meat and sprinkle the grated cheese over it. Put the whole thing in the oven and bake at 200 ° C until the rösti mixture is golden brown. (approx. 30-40 minutes)