Taken from Nigella's Pasta alla Genovese

Last Christmas, Hugh gave me Nigella Lawson's cookbook - Kitchen.  In it is a recipe for Pasta alla Genovese, which we all enjoyed on New Year's Eve.  I've made it a few times since then and it is a hit with everyone in the family.  I admit to using my own or, more often, store bought pesto.  The Costco pesto is easy and works just fine.  So below are the cooking instructions for everything but the pesto.  Serves 6-8.

Pasta alla Genovese

500g floury potatoes, slices 1 1/2 cm think and cut into chunks
500g pasta
200g green beans, trimmed and halved
approx 1 c good quality pesto

1. Put the prepared potato chunks into a large saucepan with enough salted water to take the pasta later, and bring to the boil.
2. Cook the potatoes until tender, about 20 minutes, then add the pasta. Check the packet cooking instructions, and at about 4 minutes before the end of the specified cooking time, add the green beans.  Cook the remaining 4 minutes.
3. Before you drain the saucepan, remove and reserve about 1/2 cupful of the cooking liquid. Drain the potatoes, beans and pasta, and put them back into the dry pan.
4. Add pesto and enough cooking water to give a runny sauce that coats the pasta. Serve immediately.