Emily's Purloined Beet and Lentil Salad

6 medium beets, unpeeled, scrubbed, trimmed
1 medium onion (red or yellow), quartered lengthwise, sliced into 1/3 inch slices
20 basil leaves, torn
4 cloves garlic, crushed
⅓ cup olive oil
½ cup water
½ teaspoon salt
Freshly ground black pepper
3 cups lentils, picked over and rinsed
4 to 5 cups chicken stock
Simple mustard vinaigrette (below)

6 to 8 servings

Preheat oven to 425 degrees. Place whole beets into a 13 x 9 x 2-inch baking dish; strew with onion slices, basil leaves, crushed garlic. Drizzle with olive oil; salt, pepper. Add water to pan.
Cover pan tightly with foil, bake without uncovering, for 1 hour and 15 minutes.
While beets are roasting, place lentils in another 13 x 9 x 2-inch pan with 4 cups of the stock, tightly covered with foil. After the beets have cooked for 45 minutes, place lentils in oven. Check lentils after 30 minutes. If stock has been absorbed and lentils are tender, remove with beets. Otherwise, continue to cook another 15 minutes or so, adding more broth if necessary to prevent lentils from burning.
Allow beets and lentils to cool, uncovered. (Drain any excess broth from lentils if necessary) Remove beets from pan, reserving remaining beet-juice-onion-basil mixture. Peel, cut into 1-inch chunks; combine with lentils and juice-onion-basil mixture in a large bowl. Toss with about half jar of Simple mustard Vinaigrette, more or less to taste. Adjust salt and pepper. Serve at room temperature.
To make vinaigrette: In a jar, stir together 8 tablespoons olive oil, 1 tablespoon Dijon mustard, 3 tablespoons of red wine vinegar, 1/2 teaspoon salt, freshly ground black pepper. Place the lid on the jar, and shake vigorously, until emulsified.

3 hours