Preheat oven to 350°F. Lightly grease a casserole dish with olive oil. Set aside.

Bring a large pot of salted water to a rolling boil over medium heat.

Add broccoli florets and cook 2 minutes. Scoop broccoli out of water with a spider skimmer or slotted spoon into a colander. Rinse with cool water to stop cooking.

Add pasta shells to boiling water and cook according to package directions just until al dente.  Reserve 1/2 cup of pasta water and set aside.

Drain cooked shells and run under cool water to prevent overcooking.

In the meantime, melt butter in a medium saucepan over medium heat. Add minced garlic, whole milk, and heavy cream. Bring to a simmer.

Remove from heat and stir in parmesan and 1 cup of mozzarella cheese. Whisk until the cheese is all melted and the sauce is smooth. Season with salt and pepper to taste.

Rough chop broccoli and add to a medium mixing bowl.

Add shredded chicken, garlic powder, parsley, and the alfredo sauce. If mixture seems too thick, add a bit of pasta water to thin out (2 Tablespoons should do it).

Toss together with a large spoon. Season with salt and pepper, to taste.

Fill each pasta shell with a tablespoon of the chicken alfredo mixture and arrange them in the prepared baking dish. Spread any leftover stuffing mixture on top of the shells and cover with the remaining mozzarella cheese.

Bake pasta shells uncovered until golden-brown and bubbly, 20-25 minutes. Let cool 5 minutes, then serve and enjoy!