Cut the runner beans and potatoes into small pieces. Put all the ingredients (except those for the vinaigrette) into the steam case. Close the case and cook in the microwave for 10 minutes at maximum power (800W). Remove the case from the microwave and make sure that the vegetables are cooked. If they are still a little hard, leave to rest in the case with the lids closed for 1 minute. Mix all the ingredients for the vinaigrette together well and use it to dress the runner beans and potatoes. Tip: You can also accompany this dish with a spoonful of mayonnaise and grated hard-boiled egg.