Potato Salad and Smoked Trout with Horseradish and Chives

Scandinavians frequently combine potent smoked fish and mild, creamy potatoes. For this dish, we find a modest amount of sour cream both binds the salad and adds a tanginess that, along with the pungency of the horseradish, works well with the salty richness of smoked trout. Up the horseradish if you like. Tossing the potatoes with vinegar, salt and pepper immediately after draining them allows them to soak up the seasonings as they cool so that they're flavorful throughout. Serve the salad on a bed of watercress, lettuce or your favorite greens. Leftovers can be refrigerated for a couple days; bring to room temperature before serving.