In a large skillet, heat olive oil over medium-high heat. Add chicken breasts, season with salt, pepper, and sear for 5-7 minutes on each side until golden and cooked through.

Remove chicken from skillet and set aside. To the same skillet, add white wine and garlic, cooking for 1 minute while scraping the bottom.

Stir in half-and-half and Dijon mustard, whisk until combined. Add Parmesan cheese and stir until melted.

Return chicken to the skillet, spoon sauce over it, and simmer for 3-5 minutes to allow flavors to meld. Garnish with parsley if desired.