Crème fraîche makes these potatoes extra rich and utterly delicious.
Cook potatoes in large pot of boiling salted water until very tender, about 25 minutes. Drain well. Return potatoes to pot; mash over low heat until almost smooth. Add crème fraîche and butter; whisk until smooth and fluffy. Stir in dill. Season with salt and pepper. (Potatoes can be made 2 hours ahead. Cover and let stand at room temperature. Rewarm over low heat, stirring frequently.)
Top potatoes with caviar and serve.