Only four ingredients—radishes, salt, pepper, and crème fraîche—yet they make an extremely tasty raw vegetable first course. If you can, make it with the wonderfully sharp black radishes, still relatively scarce in the States but available at some farmers’ markets. Or use a combination of red radishes, daikon, or pink-and-green-striped watermelon radishes. You can even use tender young turnips. The only work is in the slicing. A mandoline is the best tool to ensure the slices are uniformly thin.