1 1/4 pounds thick-sliced bacon, cut crosswise into 1/4-inch strips
2 tablespoons extra-virgin olive oil
1 Spanish onion, finely chopped
1 large carrot, finely diced
2 celery ribs, finely diced
4 garlic cloves, minced
1 fresh bay leaf
2 teaspoons chopped thyme
2 teaspoons chopped rosemary
1 pound Great Northern beans, soaked overnight and drained
10 cups chicken stock
Salt and freshly ground pepper
In a large soup pot, cook the bacon over moderate heat, stirring, until browned and crisp, about 7 minutes. Drain, reserving the fat and bacon separately.
Heat the olive oil in the soup pot. Add the onion, carrot and celery and cook over moderate heat, stirring occasionally, until the vegetables are softened, about 8 minutes. Stir in the garlic, bay leaf and 1 teaspoon each of the chopped thyme and rosemary and cook until fragrant, about 2 minutes. Add the drained beans, stock and 3 tablespoons of the reserved bacon fat and bring to a boil. Simmer the soup over moderately low heat until the beans are tender, about 1 1/2 hours.
Discard the bay leaf and stir in the remaining thyme and rosemary. Season the soup with salt and pepper and transfer to shallow bowls. Garnish the soup with the bacon and serve.
MAKE AHEAD The soup and bacon can be refrigerated separately for up to 3 days. Recrisp the bacon before serving.