Season the chicken with the salt, pepper, and garlic powder.
Heat the olive oil in a large deep skillet or Dutch oven over medium-high heat. Add the chicken and cook for 4 to 5 minutes until lightly browned. Transfer to a plate.
Melt the butter in the same skillet. Add the mushrooms and cook for 8 to 10 minutes, stirring occasionally, until their moisture evaporates and they become deeply golden brown.
Add the diced onion and cook for 4 to 5 minutes until softened.
Stir in the garlic and cook for 30 seconds until fragrant.
Add the rice and cook for 2 to 3 minutes, stirring frequently to lightly toast the grains.
Pour in the chicken broth. Add the thyme and Worcestershire sauce and stir well.
Bring the mixture to a gentle boil. Reduce the heat to low, cover, and cook for 10 minutes.
Return the chicken and any accumulated juices to the skillet. Cover and continue cooking for 8 to 12 minutes, or until the rice is tender and the chicken is fully cooked.
Remove the skillet from the heat. Stir in the heavy cream and Parmesan cheese until smooth and creamy.
Stir in the lemon juice and parsley.
Let the dish rest for 5 to 10 minutes before serving. Taste and adjust seasoning if needed.