Preheat oven to 425ºF. Heat the oil in a wide pot over medium-high heat. Pat the chicken dry and season all over with salt and pepper. Place in the pot, skin-side down, and cook for 5-6 minutes or until the skin is golden brown and crispy. Flip and cook 1-2 minutes more. Transfer to a plate.
Cook the Onion:
Add the onion to the pot and cook for 4-5 minutes until softened.
Cook the Mushrooms:
Melt the butter into the pot. Once melted and frothy, add the mushrooms and cook for 10-15 minutes until the mushrooms release their liquid and the liquid evaporates and the mushrooms turn deep golden brown. Season with salt, pepper, and dry thyme and toss to coat.
Simmer the Stewed Mushrooms:
Pour in the chicken stock and peppers and tomatoes and bring to a boil. Cook for 4-5 minutes or until the liquid reduces slightly. Taste and season with salt and pepper.
Bake the Chicken:
Arrange the chicken on top of the mushrooms and transfer to the oven. Bake for 20-25 minutes or until the internal temperature reaches 165ºF. If desired, turn on the broiler for the last two minutes to crisp up the skin again.
Cook the Rice:
While the chicken bakes, cook the rice according to package instructions or prepare your favorite side dish, such as buttered noodles, boiled potatoes, or sautéed green beans.
Remove the chicken from the oven and sprinkle with parsley. If serving with rice, spoon the mushrooms over the rice and place the chicken on top. Garnish with a touch more parsley. Enjoy!
If you don't have Oliverio peppers and tomatoes, use a 14.5-ounce can crushed or diced tomatoes, 1 cup diced roasted red peppers, and crushed red pepper to taste.