Heat the olive oil in a 4-quart low-sided soup pot or Dutch oven over medium to medium-high heat. Add the onion and pancetta and saute until the onion is softened and both are browned, about 12 minutes. Add the garlic, stir, and saute until fragrant, 30 seconds to 1 minute. Add the escarole and stir thoroughly to coat the leaves (and to deglaze the pan slightly with their moisture). Season with 1/2 teaspoon of the salt and a few grinds of fresh pepper. Add the stock, stir well, and bring to a boil; cover the pot, lower to a simmer, and cook 8 to 10 minutes. Uncover the pot, add the beans, and simmer another 2 to 3 minutes. Add the lemon juice and turn off the heat. Ladle the soup into four shallow soup bowls and top each with 1 tablespoon of the cheese and a quarter of the croutons.

Heat 2 tablespoons extra-virgin olive oil in a nonstick skillet over medium-high heat. Add 2 cups (lightly packed) 3/4-inch cubes of bread, cut from a good, airy, crusty loaf like ciabatta. Stir to coat the cubes with the oil, season with salt, and saute, stirring constantly, until crisp and browned on most sides, 2 to 4 minutes.