In a large saucepan, cook the green beans and carrot in a small amount of boiling, lightly salted water for 10 minutes.
Add the asparagus and broccoli, return to a boil, and cook for about 5 more minutes, or until the vegetables are crisp-tender.
Drain well and set aside.
Meanwhile, cook the pasta according to package directions. During the last 3 minutes of cooking, add the sweet pepper and zucchini to the pasta water.
Drain the pasta and vegetables, then return them to the hot pot.
Add the cooked bean mixture, cover, and keep warm.
To make the sauce, melt the butter in a medium saucepan over medium heat.
Add the onion wedges and minced garlic, cooking for 5 to 8 minutes until tender.
Pour in the vegetable broth and bring to a boil.
In a small bowl, whisk together the whipping cream and flour until smooth. Slowly pour this cream mixture into the simmering broth, stirring constantly.
Cook and stir until the sauce has thickened and is bubbly.
Remove the sauce from the heat and stir in the 1/2 cup (480 ml) of Parmesan cheese, green onions, and basil.
Continue stirring for 1 minute until the cheese is melted and the sauce is smooth.
Pour the sauce over the pasta and vegetable mixture and toss gently to combine everything.
Serve immediately on a large platter, sprinkled with additional Parmesan cheese if desired.
Before draining the pasta, reserve about 1/2 cup (480 ml) of the starchy cooking water. If your sauce is too thick, you can stir in a tablespoon or two of the pasta water to reach the perfect consistency.
