olive oil -- for the pan and for sprinkling 4 large russet potatoes salt, to taste 1 cup creme fraiche -- or sour cream 1 tablespoon chopped fresh dill or parsley 1 scallion, finely chopped 1 lemon zested 6 ounces thinly sliced smoked salmon
Set the oven at 450 degrees. Generously oil 2 large rimmed baking sheets.
Using a mandoline or another hand-held slicing machine, thinly slice 2 of the potatoes lengthwise. Set the slices on the baking sheets without overlapping. Brush with olive oil and sprinkle with salt. Turn and brush the other side with oil, then sprinkle with salt.
Roast the potatoes for 10 minutes. Remove from oven and let them cool in the pan for 2 minutes. Use a metal palette knife to slide under the slices and dislodge them.
Carefully turn the slices and return them to the oven. Continue roasting for 10 minutes or until golden, checking the slices often so they do not burn. Remove the slices from the pan as they brown.
Slice and roast the remaining potatoes.
In a bowl, whisk the creme fraiche or sour cream until it is smooth. Beat in the dill or parsley, scallion, lemon rind, and salt.
Cut the salmon into pieces about the size of the largest potato slices.
To assemble: On each salad plate, layer 3 potato slices with 2 pieces of salmon, beginning and ending with the potato. Pass the creme-fraiche or sour-cream sauce separately.