Stelline, Borlotti Bean and Rocket Soup

3 tablespoons olive oil
1 leek, thinly sliced
1 small fennel bulb, thinly sliced
4 rashers streaky bacon, thinly sliced
2 cloves garlic, crushed
2 teaspoons finely chopped rosemary
6 cups good quality chicken stock
1⁄2 cup stelline or other very small pasta
1 x 400 gram tin cooked borlotti beans, drained and rinsed
2 handfuls rocket leaves
sea salt and freshly ground pepper
1⁄2 cup fresh basil
shaved Parmesan to serve