1. Bring a large pot of water to a boil. Blanch the potatoes for 2 minutes. Drain, then plunge into cold water and drain again. Pat dry with paper towels.
2. When cool enough to handle, cut the potatoes in half. Using a melon baller, scoop out and discard the centers.
3. Heat the oil in a deep pot or fryer to 350 F. Fry, 8 potato halves at a time, until golden brown all over. With a slotted spoon, transfer to paper towels to drain.
4. In a small bowl, mix together the crème fraîche and lemon juice. Place a dollop of the mixture into the potatoes and spoon the caviar on top.