1Heat olive oil in a large skillet over medium-high heat. Season chicken breasts with salt and pepper, then add to the skillet. Cook 6–7 minutes per side until golden brown and cooked through. Remove chicken and set aside.
2In the same skillet, add the chopped onion and garlic. Sauté until onion is translucent, about 3–4 minutes.
3Pour in the whiskey, scraping the bottom of the skillet to deglaze. Let simmer for 2 minutes to reduce slightly.
4Stir in chicken broth, heavy cream, and Dijon mustard. Bring to a gentle simmer and cook for 5 minutes, until the sauce thickens slightly.
5Return chicken to the skillet and spoon sauce over the top. Simmer for 2–3 minutes to heat through.