Boil chicken breasts and broccoli crowns in a pan for about 35 minutes.

Drain the chicken and broccoli mixture.

Add the drained mixture to a deep mixing bowl.

In the mixing bowl, add chopped mushrooms and Parmesan cheese.

Using a hand mixer, shred the chicken and combine all ingredients on low speed, adding about 1/2 cup of water to aid in shredding.

Boil the noodle shells with a tablespoon of butter until al dente.

Drain the cooked noodles and let them cool.

Grease a deep casserole dish.

Fill each noodle shell with the chicken and vegetable mixture.

Place the stuffed shells in the prepared casserole dish.

Once the dish is filled with stuffed shells, top with Alfredo sauce.

Sprinkle the shredded cheese evenly over the Alfredo sauce.

Heat the Alfredo sauce before pouring over the stuffed shells for even distribution.

Cover the casserole dish with aluminum foil.

Bake in a preheated oven at 375°F (190°C) for 45 minutes.

Remove the casserole dish from the oven and let it cool for about 20 minutes before serving.