Place a large, deep saucepan over medium and add the olive oil along with the onions. Sauté for 3-4 minutes, increase the fire and add the cut courgettes. Season with half of the salt and pepper and keep sautéing until soft, about 5 minutes. Keep aside.
In the meantime, place a large pot filled with the water to a boil on high heat, adding a generous amount of salt. Add the pasta, stirring occasionally so as not to stick and cook 2 minutes less than package instructions.
Put the cooked zucchini along with the basil leaves in a food processor with the metal blade attached, along with the mascarpone cheese and 150 ml of the chicken broth, season with the remaining salt and pepper. Pulse couple of times and keep aside.
Put the same saucepan that the courgettes were sautéed over low heat and add the zucchini cream along with the smoked salmon. Strain the pasta and return to the pan. Toss the pasta so as the sauce goes to every single piece of the pasta and add the remaining chicken broth if consistency is on the thick side. Serve and top with the Parmigianno Reggiano cheese.