Preheat your oven to 350°F (175°C).

Bring a large pot of salted water to a boil and cook the manicotti shells for 6–8 minutes until al dente. Drain and cool.

In a skillet, cook diced chicken over medium heat for 5–7 minutes until no longer pink, seasoning with salt and pepper.

Combine cooked chicken, ricotta cheese, grated Parmesan, chopped parsley, salt, and pepper in a bowl.

Fill each manicotti shell with the chicken and cheese mixture.

In a saucepan, melt butter, add garlic, and sauté. Whisk in heavy cream and thicken, then mix in remaining Parmesan.

Spread a thin layer of Alfredo sauce in the baking dish and arrange the filled shells. Pour the remaining sauce over the shells.

Cover with foil and bake for 30 minutes. Remove foil and bake for an additional 10–15 minutes until golden.

Let sit for 5 minutes, garnish with parsley, and serve warm.