Peel the potatoes and process them while they are still lukewarm. Halve small potatoes and quarter larger ones (no slices). Cut the spring onions into rings. Cut the eggs into slices, cut the feta into large cubes and add everything to the potatoes. Add olives, parsley, dill and possibly mint. Mix the olive oil with the lemon juice and the yoghurt (e.g. in a blender). Add anchovies to the salad and pour the dressing over it. Mix carefully and let steep for at least 1 hour.