I like the slightly bitter edge frisée gives to the salad, but I use it as much for looks as flavor, since it mounds so well and looks so festive. Other greens like arugula or a mesclun mix would taste good, too.
In a small bowl, whisk the olive oil and the lemon juice. Season to taste with salt and pepper.
Put the frisée in a medium bowl. Trim, quarter, and core the fennel bulb. Using a vegetable peeler or mandoline, shave the fennel lengthwise until you have about 1 cup (you may not need the whole bulb). Add the fennel to the frisée and toss with just enough of the vinaigrette to moisten the leaves.
Toss the beets and chives with enough of the remaining vinaigrette to coat. Divide about half of the diced beets among four large salad plates. Divide the frisée among the plates, mounding it over the beets. Sprinkle the remaining beets and the feta on top of the frisée. Finish each plate with a tiny pinch of fleur de sel if you like, and serve.
Photo: Scott Phillips