Cook the Chicken:
Season the chicken breasts on both sides with salt, pepper, garlic powder, and onion powder. Heat olive oil or butter in a large skillet over medium heat. Cook the chicken for 5-7 minutes per side, or until golden brown and fully cooked (internal temperature of 165°F). Remove from the skillet and set aside.
Make the Gravy:
In the same skillet, melt the butter over medium heat. Stir in the flour and cook for 1-2 minutes, whisking constantly, until golden brown. Gradually whisk in the chicken broth, ensuring no lumps remain. Add Worcestershire sauce, dried thyme (if using), and a pinch of salt and pepper. Let the gravy simmer for 3-4 minutes until thickened. Return the chicken to the skillet, spooning gravy over the top.
Cook the Potatoes:
Place the peeled and cubed potatoes in a medium saucepan, cover with water, and add a pinch of salt. Bring to a boil and cook until fork-tender (about 15-20 minutes). Drain and return to the pot.
Mash the Potatoes:
Add milk, butter, salt, and pepper to the potatoes. Mash until smooth and creamy using a potato masher or hand mixer. Adjust the seasoning as needed.
Assemble the Plate:
Serve the chicken and gravy over a generous scoop of mashed potatoes. Pair with a side of green beans, roasted vegetables, or a fresh salad for a complete meal.