1. Start by heating 1 tablespoon of olive oil in a skillet over medium heat. Add the chopped onion and sauté until softened, about 3-4 minutes. Then, stir in the minced garlic, Italian seasoning, salt, and pepper, and cook for another minute to let the flavors bloom. Next, add the sliced baby bella mushrooms and cook until they’ve softened and any excess liquid has evaporated, approximately 5-7 minutes. Transfer the mushroom mixture to a bowl and let it cool slightly. Finally, fold in the cream cheese, shredded provolone, and chopped chives until the filling is well combined.

2. Preheat your oven to 375°F. Take each chicken breast and carefully cut a wide pocket into the side, being cautious not to cut all the way through. Stuff each pocket with the prepared mushroom filling, securing the chicken with toothpicks as needed.

3. In a small bowl, combine the kosher salt, onion powder, garlic powder, paprika, and ground black pepper. Sprinkle this seasoning mix generously over the stuffed chicken breasts, ensuring even coverage.

4. Heat 2 tablespoon of olive oil in a large skillet over medium-high heat. Add the stuffed chicken breasts and sear for 3-4 minutes per side until they’re nicely browned but not fully cooked through. Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the internal temperature of the chicken reaches 165°F.

5. Remove the toothpicks, if used, and let the mushroom-stuffed chicken rest for a few minutes. Serve the juicy, flavorful breasts hot, with your choice of delectable side dishes to complement the dish.