Season the chicken breasts with salt and pepper. Heat olive oil in a skillet over medium-high heat and cook chicken for 6–7 minutes on each side until golden brown. Transfer to a plate and keep warm.

In the same skillet, sauté the chopped onion over medium heat for 3–4 minutes until soft. Add minced garlic and cook for 1–2 minutes.

Pour in the whiskey and scrape the bottom of the skillet. Simmer for 5 minutes.

Add chicken broth and simmer for another 5 minutes.

Reduce heat and stir in heavy cream. Mix until well combined.

Incorporate Dijon mustard and thyme. Simmer gently for 3–4 minutes.

Add the cooked chicken back into the skillet, coating well with sauce. Heat through for 2–3 minutes.

Remove from heat and stir in butter until melted. Serve with garnish.