Sear the Chicken:
Season chicken with salt and pepper. Heat olive oil and butter in a large skillet over medium-high heat.
Sear chicken for 5–6 minutes per side until golden and cooked through. Remove and set aside.
Sauté Garlic:
In the same pan, reduce heat to medium. Add garlic and cook for 1 minute until fragrant.
Deglaze and Simmer:
Pour in chicken broth and scrape up any browned bits. Let simmer for 2–3 minutes to reduce slightly.
Make the Sauce:
Stir in heavy cream, Dijon mustard, whole grain mustard, and thyme. Simmer gently for 3–4 minutes until the sauce thickens slightly.
Return Chicken:
Return the chicken to the skillet and coat with the sauce. Simmer 2–3 more minutes to reheat. Add lemon juice if desired.
Serve:
Garnish with fresh parsley. Serve with mashed potatoes, roasted vegetables, or rice.