Follow these steps carefully to achieve a perfectly cooked Creamy Garlic Mushroom Chicken with a sauce that is out of this world. Take your time with each step, as building flavor along the way is key to the success of this dish.

1. Prepare the Chicken:
   • Pat the chicken thighs completely dry with paper towels. This is a crucial step for achieving a beautiful golden-brown sear. Excess moisture will cause the chicken to steam rather than sear.
   • Season both sides of the chicken thighs generously with salt and freshly ground black pepper. Don’t be afraid to season well, as this is your first opportunity to build flavor directly into the chicken.
2. Sear the Chicken:
   • Heat the olive oil in a large, heavy-bottomed skillet or Dutch oven (cast iron works wonderfully here) over medium-high heat. The pan needs to be hot enough to sear the chicken quickly. You’ll know it’s ready when the oil shimmers or a drop of water evaporates instantly.
   • Carefully place the seasoned chicken thighs in the hot skillet, ensuring not to overcrowd the pan. If necessary, cook the chicken in two batches. Overcrowding will lower the pan temperature and result in steamed, rather than seared, chicken.
   • Sear the chicken for about 4-5 minutes per side, without moving them around too much. You’re looking for a deep golden-brown crust to develop. This crust (the Maillard reaction) is packed with flavor.
   • Once seared, remove the chicken from the skillet and set it aside on a clean plate. The chicken will not be fully cooked through at this point; it will finish cooking in the sauce later. Don’t clean the skillet; those browned bits left behind are flavor gold!
3. Sauté Mushrooms and Aromatics:
   • If needed, add a touch more olive oil (or the optional tablespoon of butter) to the same skillet. Reduce the heat to medium.
   • Add the sliced cremini mushrooms to the skillet. Spread them in a single layer as much as possible. Allow them to cook undisturbed for 3-4 minutes until they start to brown and release their moisture. Then, stir and continue to cook until they are nicely caramelized and their liquid has mostly evaporated (about 5-7 minutes total). This browning step is essential for developing their deep, earthy flavor.
   • Add the finely chopped yellow onion to the skillet with the mushrooms. Sauté for another 3-4 minutes, stirring occasionally, until the onion softens and becomes translucent.
   • Stir in the minced garlic and dried thyme (if using dried). Cook for about 1 minute more, stirring constantly, until the garlic is fragrant. Be very careful not to burn the garlic, as it can become bitter.
4. Deglaze and Build the Sauce Base (Optional Flour):
   • If you’re using flour for a thicker sauce, sprinkle the 1 tablespoon of all-purpose flour over the mushroom and onion mixture. Stir constantly and cook for 1 minute. This cooks out the raw flour taste.
   • Pour in the dry white wine. Bring it to a simmer, scraping up any browned bits (fond) from the bottom of the pan with a wooden spoon or spatula. This deglazing process incorporates all those concentrated flavors into the sauce. Let the wine simmer and reduce by about half, which should take 2-3 minutes. This cooks off the harsh alcohol flavor, leaving behind its fruity complexity.
5. Create the Creamy Sauce:
   • Gradually pour in the chicken broth, stirring continuously to combine with the mushroom mixture (and flour, if used) to ensure a smooth sauce. Bring the mixture to a gentle simmer.
   • Reduce the heat to low and stir in the heavy cream and grated Parmesan cheese. Continue to stir gently until the Parmesan cheese is melted and the sauce is smooth and slightly thickened. If you used flour, it will thicken more readily.
   • Taste the sauce at this point and season with salt and pepper as needed. Remember that the chicken is already seasoned, and Parmesan adds saltiness.
6. Finish Cooking the Chicken:
   • Return the seared chicken thighs (and any accumulated juices from the plate – more flavor!) to the skillet, nestling them into the creamy mushroom sauce.
   • Ensure the sauce is at a gentle simmer, not a rolling boil. Cover the skillet and let the chicken cook for another 10-15 minutes, or until the chicken is cooked through and the internal temperature reaches 165°F (74°C) when checked with a meat thermometer. The exact time will depend on the thickness of your chicken thighs.
   • If the sauce becomes too thick during this simmering process, you can add a splash more chicken broth or water to reach your desired consistency.
7. Final Touches and Serve:
   • Once the chicken is cooked through, turn off the heat. If using fresh thyme, stir it in now along with the chopped fresh parsley.
   • If you’re using the optional tablespoon of butter for extra richness, stir it into the sauce now until melted.
   • Let the dish rest for a few minutes before serving. This allows the flavors to meld further.
   • Serve the Creamy Garlic Mushroom Chicken hot, spooning generous amounts of the luscious sauce and mushrooms over each piece of chicken. Garnish with additional fresh parsley, if desired.

Enjoy this incredibly flavorful and comforting meal!