Bring a large pot of salted water to the boil

Add the diced potato to the boiling water

Cook for 5 minutes

Add the green beans and pasta to the potatoes cooking in boiling water

If you are using fresh pasta, give the green beans about 5 minutes to cook before you add the pasta

Cook all until pasta is al dente, at which time the vegetables should be properly cooked. While the pasta is cooking, place the pesto in a shallow serving bowl

Drain pasta, reserving some pasta water

Transfer the cooked pasta, green beans, and potato to the serving bowl containing the pesto, and toss

Add 1 to 2 tablespoons of cooking water, if necessary, to enable the pesto to coat the pasta

Serve with freshly grated Parmesan

Serves 4 to 6.