In a small bowl, combine the onion powder, garlic powder, salt and pepper. Season both sides of the chicken breasts, and set aside.
½ teaspoon onion powder, ½ teaspoon garlic powder, ½ teaspoon salt, ¼ teaspoon ground black pepper, 1 pound chicken breasts
Heat a large, deep skillet over low to medium heat. Add the butter, and cook the chicken for 5 to 6 minutes on each side until the juices run clear. A meat thermometer should read 165°F when inserted into the thickest part of the chicken. Remove the chicken from the skillet to a waiting plate.
2 tablespoons unsalted butter
Keep the skillet on low to medium, and add the butter for the gravy. Next add the mushrooms and onions. Cook for 3 to 5 minutes just until the mushrooms are soft and the onions are translucent. Use a slotted spoon to remove them from the pan, and set aside.
1 tablespoon unsalted butter, 4 ounces baby bella mushrooms, ½ cup white onion
Sprinkle the flour into the hot pan, and stir to pick up any remaining butter or liquid. Cook the flour for 2 to 3 minutes, then carefully add the chicken broth. Stir or whisk until no flour clumps remain, then add the heavy cream, oregano, rosemary, salt, pepper, and thyme.
2 tablespoons all-purpose flour, 1 cup low-sodium chicken broth, ½ cup heavy cream, ½ teaspoon dried oregano, ½ teaspoon dried rosemary, ½ teaspoon salt, ¼ teaspoon ground black pepper, ¼ teaspoon dried thyme
Continue to stir until the sauce thickens slightly and coats the back of a spoon, about 5 minutes. Remove from heat, and add the mushrooms, onions, and chicken back to the pan.
Serve hot with a side of fresh vegetables or a salad. Store any leftovers in the refrigerator for up to 3 days.