While the potatoes are still warm, remove the skin and cut them into thin strips. Remove the outer leaves and the stalks from the white cabbage, slice finely and mash the strips a little. Drain the mandarin oranges. Rinse the grapes, cut them in half and remove the seeds. Coarsely chop the walnuts. Dice the cheese. Gently mix all salad ingredients together. Pour the vinaigrette over it. Drizzle the leaf salad with the brandy and leave in the fridge for 10 min with the lid closed.