Making the Grilled Chicken Panini Sandwich is a simple process that anyone can follow. Here are the steps:

1. Prepare the Chicken: Season the chicken breasts with garlic powder, Italian seasoning, salt, and pepper. Drizzle with olive oil.
2. Grill the Chicken: Preheat your grill or pan over medium heat. Cook the chicken for about 6-7 minutes on each side or until fully cooked. Let it rest for a few minutes before slicing.
3. Assemble the Sandwich: On one slice of bread, layer the sliced chicken, mozzarella cheese, spinach leaves, and tomato slices. If desired, spread pesto or mayonnaise on the other slice of bread before closing the sandwich.
4. Press the Sandwich: Heat a panini press or grill pan over medium heat. Place the assembled sandwich on the press and close it. Grill for about 3-5 minutes or until the bread is golden brown and the cheese is melted.
5. Slice and Serve: Remove the sandwich from the press and let it cool for a minute. Slice it in half and serve warm.

These steps will guide you in creating a delicious Grilled Chicken Panini Sandwich that is sure to impress!