Prepare and Sear the Chicken: Season the chicken thighs with salt and pepper on both sides. Heat the olive oil in a large skillet over medium-high heat. Add the chicken thighs and cook for 5–6 minutes per side, or until golden brown and cooked through. Remove the chicken from the skillet and set aside.

Sauté Onion and Garlic: In the same skillet, reduce the heat to medium. Add the chopped onion and sauté for 3–4 minutes, or until softened. Add the minced garlic and cook for another minute until fragrant.

Deglaze the Skillet: Pour in the chicken broth and use a wooden spoon to scrape up any browned bits from the bottom of the pan. This adds extra flavor to the sauce.

Make the Mustard Sauce: Stir in the Dijon mustard and whole grain mustard (if using). Let the mixture simmer for 2–3 minutes to reduce slightly. Add the heavy cream and thyme, stirring well. Simmer the sauce for another 2–3 minutes until it thickens slightly.

Combine Chicken and Sauce: Return the chicken thighs to the skillet, spooning the sauce over the top. Let the chicken simmer in the sauce for 5 minutes, ensuring the flavors meld together and the chicken is heated through.

Garnish and Serve: Remove the skillet from heat and sprinkle with fresh parsley for garnish. Serve hot with your choice of side dish.