1. Preheat oven to 375-400°F.
2. Butterfly or cut chicken breasts into thinner pieces for even cooking.
3. Season chicken with salt, pepper, and garlic powder.
4. In a bowl, mix cream cheese, sour cream or Greek yogurt, and mayonnaise.
5. Stir in chopped spinach, drained and chopped artichoke hearts, and Dijon mustard if using.
6. Add mozzarella and Parmesan cheese to the mixture and combine well.
7. Spread a layer of the spinach artichoke mixture over each chicken breast.
8. Place chicken in a greased casserole dish.
9. Sprinkle additional cheese on top if desired.
10. Bake in the preheated oven for 25-35 minutes until chicken is cooked through.
11. Let it rest for a few minutes before serving.
12. Serve as is or pair with rice, pasta, or vegetables.
13. Store leftovers in an airtight container for future meals.
14. Reheat leftovers in the oven or microwave before serving.
15. Customize with additional vegetables or cheeses for variety.