Sautee the onion until softened, lightly steam the broccoli and shred the chicken.
Boil the pasta shells in plenty of salted water to just cooked (al dente)
Remove half a cup of the alfredo sauce, and set aside.
In a large bowl, combine the onions, broccoli, shredded chicken, half the cheddar cheese, salt and pepper.
Add the remaining alfredo sauce and mix well
When the pasta is cool enough to handle, spoon the mixture into the shells.
Drizzle the remaining alfredo sauce over the shells and top with the remaining cheese
Place in a greased baking dish, cover with foil and bake at 350°F for 25 minutes, then take the foil off and bake for a further 5-10 minutes.
Save time and grab a rotisserie chicken from the store, and use that instead of cooking chicken breasts from scratch.What to do with leftoversStore tightly covered with plastic wrap in the refrigerator for about 2 days. They can dry out, so you may need to add a little extra sauce when reheating.Substitutions/AdditionsIf you can't find jumbo pasta shells, no worries! Use manicotti tubes if you can find those. You could also make this lasagna style, and use no-boil lasagna sheets, laying the chicken mixture, sauce and cheeses in a baking dish.Add some fresh garlic, or garlic powder to the stuffing mixture.