1. Preheat the oven to 375 degrees F. Wrap the beets in a large piece of foil and bake for 1 to 1Â½ hours, or until tender. Let cool slightly, then peel the beets and slice them 1/4 inch thick. Using a 1-inch heart-shaped cookie cutter, cut as many hearts as possible from each slice.
2. In a large bowl, whisk the olive oil with the lemon juice, salt and pepper. Add the arugula, frisée and beets and toss. Mound the salad on plates, sprinkle with the chives and serve.
Make Ahead: The beet hearts can be refrigerated for up to 1 day.