Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking dish.

Cook the jumbo pasta shells in a large pot of boiling salted water according to package instructions until al dente (8-10 minutes). Drain and cool.

In a bowl, combine the shredded chicken, cream cheese, mozzarella, and pesto until creamy and well-mixed.

Spread 1 cup of marinara sauce in the bottom of the baking dish.

Stuff each shell with about 3 tablespoons of the chicken filling and place them seam-side up in the dish.

Pour the remaining marinara sauce over the shells and sprinkle with mozzarella.

Bake uncovered for 25-30 minutes until cheese is bubbly and golden.

Let sit for 5 minutes before serving. Garnish with parsley if desired.