In a medium skillet over medium heat, melt the butter (about 3 minutes). Add the celery and onion, and sauté until soft and fragrant, approximately 5 minutes.

In a large mixing bowl, combine the sautéed vegetables, seasoned bread cubes, and chicken broth. Add in the Italian seasoning, paprika, salt, and pepper. Stir until the bread is nicely moistened. Let it sit for about 10 minutes to absorb the flavors.

Preheat your oven to 375°F (190°C). If using an air fryer, set it to 360°F.

While the oven preheats, prepare the chicken breasts. Using a sharp knife, create a pocket in each chicken breast by slicing horizontally, being careful not to cut all the way through.

Stuff each chicken breast generously with the stuffing mixture, ensuring it is well-filled but not overstuffed.

Heat olive oil in an oven-safe skillet over medium-high heat. Season the stuffed chicken breasts with additional salt and pepper, then sear them in the skillet for about 3 minutes on each side until golden brown.

Transfer the skillet to the preheated oven. Bake for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F (75°C).

For air frying, cook for about 20-25 minutes, or until the temperature reaches the same level.

Remove the chicken from the oven and let it rest for about 5 minutes. Slice and serve warm, garnished with fresh herbs if desired!