In a medium-sized saucepan or in a double boiler, combine all the sauce ingredients. Cook over a low heat until everything is melted and the sauce is velvety smooth, about 20 minutes. Meanwhile, in a large pot of boiling salted water, cook the fettuccine to desired doneness; drain and place in a large bowl. Mix in the vegetables and sauce, and sprinkle with the Parmesan cheese. Serve immediately.