Step 1

Microwave spinach in a medium bowl until warmed through, 2 to 3 minutes. Let cool slightly and squeeze to remove excess moisture.

Step 2

Return spinach to the bowl. Mix in cream cheese, artichoke hearts, Parmesan cheese, mayonnaise, garlic powder, and salt. Set aside.

Step 3

Pound chicken breasts to an even thickness, no more than 1-inch-thick. Season with salt and pepper on both sides.

Step 4

Preheat the oven to 375 degrees F (190 degrees C).

Step 5

Heat olive oil in a large skillet over medium-high heat. Brown chicken breasts in the hot oil, 2 to 3 minutes, working in batches if necessary. Place chicken breasts in a large baking dish. Spread spinach-artichoke mixture on top of each breast.

Step 6

Bake in the preheated oven until chicken is no longer pink in the center and the juices run clear, 20 to 22 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Top breasts with the mozzarella cheese and continue baking until cheese has melted, 1 to 2 more minutes.