Preheat the oven to 350°F.

Using some of the oil, grease a roasting pan large enough to hold the leeks comfortably in a single layer. Arrange the leeks in a single layer and pour the stock over.

Bake until very tender, for about 2 hours. Fifteen minutes before the leeks are done, arrange the lemon slices over them and add the remaining olive oil.

Season with salt and pepper, and serve hot or cold.

Microwave Variation

Place the leeks in 2 layers in a 14 × 9 × 2-inch oval dish. Pour in 2 cups stock. Arrange 2 lemons, sliced as above, in an even layer over the leeks. Drizzle with the olive oil.