Creating Baked Tuscan Chicken Casserole is simple and enjoyable. Follow these steps to achieve a delicious end result:

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Sauté Chicken: Heat olive oil in a large skillet over medium-high heat. Season chicken breasts with salt, pepper, and garlic powder. Sauté for 5-6 minutes per side, until golden brown and cooked through. Set aside to cool, then shred.
3. Prepare Vegetables: In the same skillet, add chopped spinach and sun-dried tomatoes. Sauté for 2-3 minutes until spinach is wilted. Remove from heat.
4. Combine Sauce: In a mixing bowl, combine marinara sauce and heavy cream. Stir well to blend the flavors.
5. Layer Ingredients: In a 9×13 inch baking dish, layer half of the shredded chicken at the bottom. Add half of the spinach and sun-dried tomato mixture on top.
6. Add Sauce: Pour half of the sauce mixture over the layered chicken and vegetables. Sprinkle half of the mozzarella cheese and Parmesan cheese.
7. Repeat Layers: Repeat the layering process with the remaining chicken, spinach, and sun-dried tomatoes. Pour the remaining sauce over the top, finishing with the remaining cheese.
8. Bake: Cover the dish with aluminum foil and bake for 30 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbling and golden.
9. Let it Rest: Once done, remove from the oven and let the casserole sit for 5 minutes before serving. This allows the flavors to settle.
10. Serve: Garnish with fresh basil if desired, and serve warm.

These simple steps create an inviting and satisfying casserole that you and your loved ones will enjoy.