Preheat oven to 400°F (200°C).

Grease a baking dish.

Heat olive oil in a frying pan over medium heat.

Add chicken breast to the pan and sauté for 1-2 minutes on each side, until cooked through.

Remove chicken from the pan and arrange in the prepared baking dish.

In a bowl, mix together chopped parsley, chopped black olives, and chopped tomatoes.

Pour the parsley, olive, and tomato mixture over the chicken in the baking dish.

Arrange mozzarella slices on top of the tomato mixture.

Bake in the preheated oven for 25-30 minutes, or until the mozzarella is melted and bubbly and the casserole is heated through.

Let rest for 5-10 minutes before serving.