Clean, rinse and pluck the salads into bite-sized pieces. Peel the lemon, also removing the white skin. Cut the lemon into very thin slices.
For the potato cream, puree the peeled potatoes, sour cream, chervil and quark with the magic wand or in a blender. Season well with salt, pepper and cayenne pepper.
Mix the lettuce and lemon wedges and serve with the potato cream.