This soup is flavorful and satisfying, yet still very healthy.
Place navy beans in a large bowl andadd water to cover. Let soak overnight inthe refrigerator.
Fill a large bowl with cold water. Sliceleeks into 1/4-inch rounds; add to water.Let sit for about 5 to 10 minutes to rid them of dirt and sand. Lift leeks out ofwater and drain in a colander. Set aside.
In a medium, heavy-bottomed stockpot,heat olive oil over medium-low heat. Addleeks and garlic; sautÃ© until translucent,stirring occasionally, about 6 minutes.Add parsley, rosemary, thyme, carrots,potatoes, and pepper. Cover and cook,stirring occasionally, 10 to 15 minutes;lower heat if mixture browns.
Drain beans, discarding soaking liquid.Add beans and stock to vegetables. Cover, bring to a boil, and reduce heat to low;cook until beans are tender, about 40minutes. About 10 minutes before thebeans are done, add salt.
Meanwhile, heat oven to 400 degrees. SprinkleGruyere over bread. Place on a cookiesheet; toast until cheese is melted andgolden, about 10 minutes.
. Add spinach to soup; cook 1 to 2 minutes more. Divide soup among bowls andserve immediately, garnished with chervil,if desired, and Gruyere toast.
The beans can be quick-soaked instead ofsoaked overnight: Bring to a boil in asaucepan of water; boil for one minute, thenlet stand in the liquid for one hour.