Pat washed chicken thighs dry on both sides with paper towels. Season the chicken with salt and ground black pepper on both sides. Heat up an extra large pan or two regular pans. You have to fit 6 thighs in a single layer. I used 2 cast iron pans. Use just a tsp of oil to coat the bottom of the pans. Place the chicken skin side down. Leave the chicken to cook for 15 minutes. Don’t touch them or move them at all. The skin needs to turn golden brown. The heat should be medium to medium low so the chicken doesn’t burn.
Slice a large yellow onion. Wipe the mushrooms clean with a damp paper towel. Slice the mushrooms into 3 or 4 pieces. They should be thick slices, not thin. Chop up about 6 big garlic cloves.
After 15 minutes, turn the chicken over. Chicken should come off the pan easily and be golden brown. Don’t force any pieces off that aren’t ready. Cook the pieces for 15 minutes on the other side. Medium size thighs will be cooked in 30 minutes. Larger thighs will take a few more minutes.
After 15 minutes, the chicken is done, remove from the pans and set aside. If there is too much oil in the pans, remove some of it. We need just enough to sautee the onions in one pan and mushrooms in the other.
Sprinkle a little salt over the onions and sautee until soft. Sprinkle a little salt over the mushrooms and cook until golden. I’m sauteeing the mushrooms in two batches, you don’t want to overcrowd the pan or they’ll steam instead of getting a nice golden color.
When the onions are almost done, add the chopped garlic and cook until soft. When the first batch of mushrooms are golden, remove them and add the second half of the mushrooms. Sautee with a little salt. They cook very quickly.
When the mushrooms are done and the onions and garlic are done, put the onions and garlic into the pan with the mushrooms. The pan with the onions have nice crusty bits of flavor on the bottom and we don’t to waste it. Pour chicken stock into the pan and bring to a boil scraping up all the bits. Pour into the other pan. Add sprigs of fresh thyme. Add salt and ground black pepper to taste. Add apple cider vinegar for acidity. Bring it just to a boil. Mix cornstarch with cold water and add to pan. Cook for just one minute and you’ll have the perfect consistency.
You can heat the chicken over the sauce on very low heat or leave the chicken in a low oven to keep warm while you make the sauce. Since the sauce comes together pretty quickly, the chicken doesn’t even have to be heated up. It’ll stay more crispy that way. Chicken with mushrooms is perfect served over egg noodles or mashed potatoes.