Add the potatoes to a large pot and cover with water. Bring to a boil and cook until fork tender.

Once cooked, strain the water and return the potatoes to the pot. Add butter, heavy cream, and salt. Mash until smooth and creamy. Cover to keep warm.

Season both sides of the chicken breasts with salt, pepper, and garlic powder.

Melt butter and olive oil in a large skillet over medium-high heat. Add the chicken and cook for about 5 minutes until browned. Flip and cook another 5 minutes. Remove chicken to a plate.

In the same skillet, reduce heat to medium. Add butter and garlic; cook until butter is melted. Whisk in flour and let cook for one minute.

Gradually pour in chicken broth and white wine while whisking. Whisk in dijon mustard, salt, and pepper. Add heavy cream and let simmer for 1-2 minutes until slightly thickened.

Add the chicken back to the skillet with the sauce. Transfer skillet to the oven and bake for 15-18 minutes or until the chicken is fully cooked.

Serve chicken and dijon cream sauce over mashed potatoes. Garnish with parsley if desired.