Cut the potatoes into small chunks. Bring a small pan of water to the boil then blanch the potatoes for 2 minutes. Remove with a slotted spoon and set aside. Blanch the green beans for 1 minute. Refresh under cold running water and set aside. Heat 2tbsp olive oil in a large sauté pan, then add the potatoes with a good pinch of salt. Cook for a few minutes until lightly coloured. Meanwhile, bring a large pan of salted water to the boil. Cook the trofie until just tender - 9 minutes or so.
3 Spoon a small ladleful (about 2tbsp) of the cooking water over the potatoes, drain the pasta and add to the potatoes with the green beans and pesto. Stir gently to combine and coat the pasta with the Pesto, scatter over the pine nuts then serve immediately with a drizzle of oil and Parmesan, if you like.