Preheat your oven to 400°F (200°C). Season the chicken thighs with salt and pepper on both sides.
In a large oven-safe skillet, heat the olive oil over medium-high heat. Add the chicken thighs, skin-side down, and sear for about 5-7 minutes until golden brown. Flip and cook for an additional 3-4 minutes. Remove the chicken and set aside.
In the same skillet, add the chopped onion and sliced mushrooms. Sauté for about 5 minutes until softened. Add the minced garlic, thyme, and rosemary, cooking for another minute until fragrant.
Pour in the chicken broth, scraping up any browned bits from the bottom of the skillet. Stir in the heavy cream and Dijon mustard, mixing well.
Add the halved baby potatoes to the skillet, stirring to coat them in the sauce. Nestle the seared chicken thighs back into the skillet, skin-side up.
Transfer the skillet to the preheated oven and roast for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the potatoes are tender.
Remove from the oven and let it rest for 5 minutes. Garnish with fresh parsley before serving.