Pat the chicken thighs completely dry using paper towels. Drying the skin is essential for achieving a crispy crust. In a small bowl, combine the kosher salt, black pepper, and smoked paprika. Rub the chicken thighs all over with the seasoning mixture, ensuring the skin is evenly coated.

Preheat your oven to 375°F (190°C). Place a large, oven-safe skillet (cast iron or stainless steel recommended) over medium-high heat. Add 1 tablespoon of olive oil.

Once the oil is shimmering, carefully place the chicken thighs in the hot skillet, skin-side down. Sear for 6 to 8 minutes without moving, until the skin is deeply golden brown and very crispy. Flip the chicken thighs over to the flesh side and cook for an additional 2 minutes. Remove the chicken from the skillet and set aside on a clean plate, leaving the rendered fat in the pan.

Reduce the heat to medium-low. If there is more than 1 tablespoon of fat remaining in the pan, carefully pour some off. Add the 1 tablespoon of unsalted butter to the skillet. Once melted, add the minced shallot and cook for 2 to 3 minutes until softened and translucent. Add the minced garlic and cook for 1 minute until fragrant.

If using white wine, pour the ½ cup of wine into the skillet. Use a wooden spoon to scrape up any browned bits (fond) from the bottom of the pan. Let the wine simmer and reduce by half (about 2–3 minutes). Pour in the 1 cup of chicken broth and add the fresh thyme. Bring the mixture to a simmer. Whisk in the ¼ cup of Dijon mustard and the 1 tablespoon of whole grain mustard (if using) until fully incorporated and smooth.

Pour in the ½ cup of heavy cream and stir until the sauce is uniform and pale yellow. Taste the sauce and season with additional salt and pepper as needed. Return the seared chicken thighs to the skillet, placing them flesh-side down so that the crispy skin remains above the sauce.

Transfer the skillet to the preheated 375°F (190°C) oven. Bake for 15 to 20 minutes, or until the chicken thighs reach an internal temperature of 165°F (74°C) when measured with a meat thermometer at the thickest part.

Remove the skillet from the oven. Let the chicken rest in the sauce for 5 minutes before serving. Garnish generously with fresh chopped parsley before plating. Serve the chicken thighs drizzled with the creamy Dijon sauce from the pan.