Bring a large pan of salted water to the boil and cook the pasta according to the packet instructions.
Meanwhile, toast the pine nuts in a dry pan until lightly browned. Set a few aside to garnish and place the remainder in a food processor.
Steam the beans until just tender then set aside.
Reserve a few basil leaves for the garnish and add the rest to the pine nuts. Add the Parmesan and oil and blend to a coarse paste. Season with salt and pepper.
When the pasta is cooked, drain well, stir in the pesto and serve garnished with the reserved pine nuts, green beans and sliced potatoes.