Tuscan White Bean Soup

1 pound white navy beans
2 tablespoons extra virgin olive oil
3 leeks, white and tender green parts, cleaned well and chopped
1/2 onion, diced
5 celery stalks, diced
3 carrots, diced
3 garlic cloves, minced
5 cups water
5 teaspoons vegetable base (such as Better than Bouillon brand), or bouillon cubes
1 1/2 teaspoons fresh rosemary, minced
1/2 teaspoon ground black pepper
juice of 1/2 lemon
minced fresh rosemary, lemon wedges, and grated fresh parmesan cheese, for serving (optional)

Sort the beans and place them in a medium heavy pot.  Add enough water to cover the beans by two inches.  Bring to a boil and cook for 1 minute.  Turn off the heat and let the beans sit for 1 hour.  Drain and rinse the beans; set aside. 

In the same pot, heat the olive oil over medium heat.  Add the leeks and onion and cook for 5 minutes, stirring often.  Add the celery, carrots, and garlic and cook for 10 minutes more, stirring often.  Add the beans and water.  Bring to a boil, then reduce the heat to a simmer and cook for 30 minutes.  Add the vegetable base, rosemary, and pepper, and cook for 40 minutes more, until the beans are soft. 

Carefully transfer 3 cups of the soup to a blender.  Puree and return to the pot.  Stir in the lemon juice.  Add salt and pepper to taste. 

Sprinkle each bowl with a pinch of extra rosemary and serve with a lemon wedge.