Preheat oven to 375℉. Line a baking pan with parchment paper or foil and set aside.
Pat chicken dry using a paper towel, Cut slits about 1/2-inch to 3/4-inch apart, not cutting all the way through the chicken. Season the chicken inside slits, top and bottom. Place on prepared pan and set aside.
In a large bowl mix the cream cheese, garlic powder, chili flakes, chopped artichoke hearts, chopped spinach, 1/2 cups mozzarella cheese and 1/2 cup Parmesan cheese. When mixed well, start spooning mixture into the slits in chicken breasts. Top with additional shredded mozzarella.
Bake in preheated oven for 20 to 25 minutes or until the chicken reaches 165℉. Remove from oven and let stand about 5 minutes. Serve.