Bring a large pot of water to a boil. Add pasta and cook for 5 minutes. Add cauliflower florets and cook until the pasta and florets are tender, about 4 minutes more. Drain, rinse and return to the pot.

Meanwhile, heat oil in a large saucepan over medium heat. Add onion and cook, stirring, until tender, 2 to 3 minutes. Add wine and cook until reduced slightly, about 1 minute. Whisk milk, flour, salt and pepper together in a medium bowl and add to the pan. Bring to a boil over medium-high heat, stirring frequently. Cook, stirring, until thickened, about 1 minute. Reduce heat to low and stir in cheese until smooth. Stir chicken (or turkey) and mustard into the cheese sauce; cook until heated through, about 2 minutes.

Stir the sauce into the drained pasta and cauliflower. Serve sprinkled with chives (or scallion greens).

Tip: To poach chicken breasts, place boneless, skinless chicken breasts in a medium skillet or saucepan. Add lightly salted water to cover and bring to a boil. Cover, reduce heat to low and simmer gently until chicken is cooked through and no longer pink in the middle, 10 to 12 minutes.