How to Make It
In a food processor, pulse the basil leaves with the pine nuts and garlic until a paste forms. Add the olive oil and puree until smooth. Transfer the pesto to a small bowl. Stir in the 1/4 cup of Parmigiano-Reggiano and season with salt and pepper.
In a medium saucepan, cover the potatoes with water and bring to a simmer. Cook over moderate heat for about 15 minutes, until tender. Drain and let cool slightly. Cut the potatoes in half.
In a large pot of salted boiling water, cook the haricots verts until al dente. Using a slotted spoon, transfer the beans to a colander and rinse under cold water. Add the pasta to the pot and cook over high heat until al dente. Drain the pasta and transfer it to a large bowl. Add the cooked potatoes, beans and the pesto and toss well to coat. Season with salt and pepper and serve, passing additional Parmigiano-Reggiano at the table.