Trofie al Pesto Genovese

Method

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1. 1Wash the basil and dry it completely on a towel. Toast the pine nuts in a dry pan for 2-3 minutes until lightly colored and fragrant, then let them cool.
2. 2In a mortar, pound the garlic with the coarse salt to a paste, then add the pine nuts and crush them. Add the basil a little at a time, grinding with a circular motion until it becomes a bright green paste. If using a food processor, pulse in short bursts so the basil doesn't heat up and darken.
3. 3Stir in the grated cheeses, then pour in the olive oil in a thin stream, beating with a spoon. The pesto should be thick but loose and creamy.
4. 4Bring a large pot of water to a boil and salt it. If using, add the potatoes first; after 5 minutes add the pasta, and add the green beans 5 minutes before the pasta is done.
5. 5Drain the pasta 1 minute before the package time, while still al dente, saving a small cup of the cooking water first.
6. 6Loosen the pesto in a large bowl with 2-3 tbsp of hot pasta water. Add the pasta, potatoes and beans and toss quickly off the heat until silkily coated. Grate over a little more cheese and serve right away.