In a soup pot, heat the EVOO, a couple of turns of the pan, over medium-high heat. Add the pancetta or prosciutto, if using, and cook until browned, a couple of minutes. Add the zucchini, celery, carrot, onion, bay leaf and 2 cloves garlic; season with salt and pepper. Cook until the vegetables are tender, 7 to 8 minutes.
reheat the broiler and position a rack in the middle of the oven. Stir the chicken stock, beans and tomatoes into the soup and bring to a boil. Add the pasta and cook until al dente. Stir in the basil and lower the heat to low.
Meanwhile, in a small saucepan, melt the butter over low heat. Add in the remaining 1 clove garlic and swirl for a minute or so; remove from the heat.
Broil the bread on both sides until lightly toasted. Brush the bread with the garlic butter and sprinkle with the cheese and parsley. Broil to melt the cheese. Serve the soup in shallow bowls, each topped with a crouton.