Pat dry chicken with a paper towel. Seasoning both sides of the chicken with salt, garlic powder, onion powder, and pepper.
Heat vegetable oil in a large skillet over medium heat. Add chicken and cook each side for 4 minutes until brown and seared. Cover with lid and continue cooking for 8 to 10 minutes until cooked through. Longer cooking time is needed for thicker cuts. Transfer to a plate and set aside.
Melt butter in the same pan. Don't remove the drippings. Add onion and mushrooms and saute until softened. Stir in the flour and cook for 1 minute. Pour broth while scraping off the browned bits off the pan. Sprinkle thyme, if using.
Simmer until it thickens to a gravy consistency. Taste, season with salt and pepper. Remove from heat.
There are two things you can do once the gravy is ready–add in the chicken and simmer for a few minutes or just pour it over just before serving. Serve and enjoy!
Notes
Broth - you can also use 1 1/2 pc chicken/beef bouillon dissolved in hot water.