Though beets are often thought of as a winter vegetable, they are at their best now — tender and sweet, and filled with nutrients like folate, magnesium and potassium. When I come home from the farmers’ market with a bunches of beets — I like to combine different varieties, like golden beets and the pink and white striated chioggias — I try to roast them right away and to clean and blanch the greens so that they’re ready to use in recipes. Never let the vendor cut off the greens when you buy beets at the farmers’ market. The greens are essentially an extra vegetable, high in beta-carotene, calcium, iron and vitamin C. Buy your beets in their raw state; even roasted beets that don’t come in a can can’t measure up to beets you roast yourself. This summer I’ve been making a beautiful gratin with beets and their greens. It’s good cold or hot, keeps well in the refrigerator for about four days and reheats well, so it makes a good summer dish. If you can’t bear to turn on the oven during the day, make this gratin at night and store in the refrigerator for a quick dinner the next evening. Beet and Beet Green Gratin This gratin is beautiful if you pair chioggas or golden beets with red beets. It is good hot or cold. 2 bunches (6 to 8) beets (preferably one red and one golden or chioggia), with the greens (about 2 pounds beets and 3/4 pound greens) Salt to taste 3 eggs 3/4 cup low-fat milk 1 tablespoon extra virgin olive oil 2 large garlic cloves, minced 1/3 cup chopped chives (1 bunch) 2 ounces Gruyere cheese, grated (1/2 cup) Freshly ground pepper to taste 1. Roast the beets. Remove from the heat and allow to cool, then cut the ends off, slip off the skins and slice across the equator. 2. Bring a large pot of water to a boil while you stem and wash the greens in two changes of water. Fill a bowl with ice water. When the pot of water comes to a boil, salt generously and blanch the greens for about one minute. (You can also steam the greens until they wilt, one to two minutes). Transfer the greens to the ice water, then drain and squeeze out the water. Chop coarsely. 3. Heat the olive oil over medium heat in a medium skillet, and add the garlic. Cook for about 30 seconds, stirring, until fragrant. Stir in the greens. Stir together for a minute, season the greens with salt and pepper, and remove from the heat. 4. Preheat the oven to 375 degrees. Oil a 2-quart gratin or baking dish with olive oil. Beat together eggs, salt (about 1/2 teaspoon), pepper, milk, chives and the Gruyère. Gently stir in the greens and beets. Scrape into the gratin dish. Bake 35 to 40 minutes until set and lightly browned on the top. Allow to sit for 10 to 15 minutes before serving. Serve hot, warm or room temperature. Yield: Serves six. Advance preparation: I usually roast the beets and blanch the greens as soon as I get them home from the market. They will keep in covered bowls in the refrigerator for three or four days. The gratin is then quickly assembled. The baked gratin can be made a day ahead and reheated. Leftovers keep for four or five days and can be cut into small squares or diamonds for terrific hors d’oeuvres or snacks. Nutritional information per serving: 167 calories; 8 grams fat; 3 grams saturated fat; 118 milligrams cholesterol; 14 grams carbohydrates; 5 grams dietary fiber; 290 milligrams sodium (does not include salt added during cooking); 10 grams protein