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.