Combine the chicken thighs, chicken broth, olive oil, Dijon mustard, salt, minced garlic, lemon zest, and lemon juice in a large gallon-sized bag or bowl.
Seal the bag and shake gently to coat the chicken, then marinate in the refrigerator for at least 20 minutes while reserving the marinade for later use.
Heat a large skillet over medium-high heat and add the chicken thighs.
Cook the chicken for 5 to 6 minutes per side until golden brown and the internal temperature reaches 165°F.
Remove the chicken from the pan and let it rest while preparing the sauce.
Pour the reserved marinade into the pan, bring to a boil for several minutes, then reduce heat to medium and simmer until the liquid is reduced by half.
Lower the heat to medium-low and whisk in the heavy cream.
Return the chicken to the pan and cook for an additional 1 to 2 minutes until heated through.
Garnish with optional chopped parsley and fresh lemon slices before serving.
