Peel and wash the potatoes and carrots, cut them into cubes and place them in a baking dish.
Place the Kassler roll roast on the vegetables. Put some butter in the dish.
Cook on Broil Level 1 for 10 minutes, and then microwave at 600 watts for 25 minutes.
Let the roast rest for a few minutes.
Add crème fraiche to the vegetables, season and gently crush with a fork.
Tip: Also tastes great with sweet potatoes.