Preheat your oven to 400°F (200°C) and lightly spray a baking sheet with cooking spray.
Separate the onion slices into individual rings and set aside. Prepare the mozzarella cheese sticks by cutting the slices into small, manageable pieces.
Set up your breading station: place the flour in a shallow dish, beat the eggs in a second dish, and combine panko breadcrumbs with paprika, salt, and pepper in a third dish.
Dip each onion ring into the flour, ensuring an even coating, then into the beaten eggs, and finally coat thoroughly with the seasoned panko breadcrumbs. While breading, insert a small piece of mozzarella into the center of the onion ring before sealing it with the breadcrumbs.
Arrange the coated onion rings on the prepared baking sheet, cheese side up, leaving a bit of space between each. Spray lightly with cooking spray to help them crisp nicely.
Bake in the preheated oven for about 15-20 minutes, or until the coating is golden brown and crispy. Keep an eye on them to prevent burning and ensure the cheese inside melts thoroughly.
Remove the onion rings from the oven and let them cool slightly before serving. The cheese inside will be gooey and stretchy, creating a delightful surprise with every bite.
