Step 1: Prepare the Stuffing

• In a skillet over medium heat, heat 2 tablespoons of olive oil. Add sliced onions and sauté for 10-15 minutes until golden brown and caramelized.
• Add sliced mushrooms and garlic powder to the skillet. Season with salt and pepper. Cook until the mushrooms are tender and the moisture has evaporated, about 5-7 minutes. Stir in the Swiss cheese and mix until melted. Remove from heat and set aside.

Step 2: Prepare the Chicken

• Preheat the oven to 375°F (190°C).
• Place the chicken breasts on a cutting board. Using a sharp knife, cut a pocket into each breast, being careful not to cut all the way through.

Step 3: Stuff the Chicken

• Season the outside of the chicken breasts with paprika, thyme, salt, and pepper.
• Generously fill each chicken pocket with the caramelized onion and mushroom mixture.

Step 4: Bake the Chicken

• Place the stuffed chicken breasts in a greased baking dish. Drizzle a little olive oil over the top for added moisture and flavor.
• Bake in the preheated oven for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F (75°C) and is no longer pink in the center.