01 - Preheat oven to 375°F. Lightly grease a 9x13-inch casserole dish with olive oil or cooking spray.
02 - In a large skillet over medium heat, warm the olive oil. Sauté the diced onion until softened and translucent, about 4 minutes. Add the minced garlic and cook for an additional 1 minute until fragrant.
03 - Add the chopped spinach to the skillet and cook, stirring occasionally, until wilted if using fresh, or heated through if using frozen. Remove from heat and set aside.
04 - In a large mixing bowl, combine the softened cream cheese, sour cream, chicken broth, salt, black pepper, and dried Italian herbs. Stir until smooth and well blended.
05 - Fold the shredded chicken, chopped artichoke hearts, spinach mixture, half of the mozzarella, and half of the Parmesan cheese into the cream base. Mix until evenly distributed.
06 - Transfer the mixture into the prepared casserole dish, spreading it out in an even layer. Top with the remaining mozzarella and Parmesan cheeses.
07 - Sprinkle the breadcrumbs evenly over the cheese layer to create a golden, crispy crust.
08 - Bake uncovered for 25–30 minutes, or until the casserole is bubbly and the top is golden brown.
09 - Remove from the oven and let the casserole rest for 5 minutes before serving to allow the filling to set.