Salt & pepper

Pick any bits of shell out of the crabmeat and set aside. Cut the potatoes into thirds, place in a medium saucepan, cover with salted water, and bring to a boil over medium-high heat. Cook until tender, about 20 minutes. Drain and, when cool enough to handle, peel and cut into 1/4 inch-thick slices.
in a small bowl, combine mayonaise, sour cream, and the lemon juice; season to taste with salt and freshly ground pepper. Finely chop 2 whole scallions and a few sprigs of parsley.

To serve: Arrange several slices of potato on a platter and season with salt and pepper. Smooth some dressing on top, sprinkle with scallions and parsley, then add a layer of crab. Repeat, making several layers and ending with crab on top.