1. Place the potatoes in a large pot of salted water and boil until fork tender, about 15 to 18 minutes.

2. Drain the potatoes well, then mash with 2 tablespoons butter, warm milk, 1/4 cup of the heavy cream, 1/2 teaspoon salt, and 1/4 teaspoon black pepper until smooth and fluffy. Cover and keep warm.

3. Pat the chicken dry and season both sides with the remaining salt, remaining black pepper, onion powder, and Italian seasoning.

4. Heat the olive oil and 1 tablespoon butter in a large skillet over medium heat. Sear the chicken for 4 to 5 minutes per side until golden and nearly cooked through, then transfer to a plate.

5. In the same skillet, melt the remaining 1 tablespoon butter and add the garlic. Cook for 30 seconds until fragrant.

6. Pour in the chicken broth and scrape up the browned bits from the pan. Stir in the remaining heavy cream and Parmesan cheese, then simmer for 3 to 4 minutes until the sauce thickens slightly.

7. Return the chicken to the skillet and spoon the sauce over the top. Simmer for 4 to 5 minutes until the chicken is fully cooked and tender.

8. Sprinkle with fresh parsley and serve the chicken and sauce over warm mashed potatoes.