To make the pesto sauce, puree the basil leaves, pine nuts, almonds, and garlic in a food processor while pouring the olive oil through the feed tube opening in a slow steady stream. After oil is incorporated, process for 15 seconds more. Season with salt and pepper and process for another 10 seconds. Set aside.

Bring the broth to a boil in a medium saucepan next to the burner where you will cook the risotto. While cooking the risotto, keep the broth at a low boil.

Heat the oil and 2 tablespoons of the butter in a medium heavy-bottomed saucepan. Stir in the onion and zucchini and cook over medium heat for 5 minutes, stirring often. Season with salt and pepper. Stir in the rice and cook for about 2 minutes, stirring constantly. Add ½ cup of the simmering broth and cook, stirring constantly, until the broth has been absorbed. Add another ½ cup of the simmering broth and cook, stirring constantly, until the broth has been absorbed. Continue cooking the risotto in the same manner until only about 1 cup of the broth remains, then stir in ½ cup of the remaining broth with the pesto and potatoes. Continue cooking until the last of the broth has been absorbed. From the time the rice is added, the whole process should take 18 to 20 minutes.

When the risotto is done, remove it from the heat and stir in the remaining 2 tablespoons of butter and the Parmesan cheese. Serve at once and pass the Parmesan.