Peel and cut the potatoes into even chunks. Place them in cold salted water and bring to a boil.
While the potatoes cook, pat the chicken dry and season both sides with garlic powder, paprika, Italian seasoning, salt, and pepper.
Heat olive oil in a large skillet over medium-high heat. Sear the chicken for 5 to 7 minutes per side and cook to 165°F (74°C). Rest the chicken.
Drain the potatoes and mash with butter, warm milk, salt, and pepper until creamy.
Make the pan sauce in the same skillet by melting butter, whisking in flour, then slowly adding chicken broth and Worcestershire sauce. Simmer until slightly thickened.
Serve the chicken with mashed potatoes and spoon the warm pan sauce over the top.