Preheat the oven to 375°F. Lightly grease a 9 × 13-inch baking dish.

Season both sides of the chicken breasts with the salt, black pepper, and onion powder.

Heat the olive oil in a large skillet over medium-high heat. Sear the chicken for 2–3 minutes per side until lightly browned. Transfer it to a plate; it will finish cooking in the oven.

Reduce the heat to medium and melt the butter in the same skillet. Add the sliced onions and cook for 15–20 minutes, stirring occasionally, until soft and golden brown.

Add the garlic and thyme. Cook for 30 seconds, then stir in the beef broth and Worcestershire sauce. Scrape up the flavorful browned bits from the bottom of the skillet.

Spread the rinsed and drained jasmine rice evenly inside the prepared baking dish. Pour the onion and broth mixture over the rice and stir gently.

Arrange the chicken breasts over the rice. Cover the baking dish tightly with foil.

Bake for 40–45 minutes, or until the rice is tender and the chicken reaches an internal temperature of 165°F.

Remove the foil and place the Swiss cheese over the chicken. Sprinkle the mozzarella over the casserole.

Return the casserole to the oven uncovered for 5–10 minutes, until the cheese is melted and lightly golden.

Let it rest for 10 minutes so the rice can absorb the remaining juices. Garnish with parsley before serving.