Recipe has been scaled from original by 0.25x. Adjust cook times and pan sizes accordingly.
Preheat oven to 400 F (200 C).
Season chicken on all sides with salt and ground black pepper.
Heat olive oil over medium-high heat in an ovenproof skillet. Place chicken skin-side down in skillet and cook until browned, about 5 minutes.
Turn chicken over; stir mushrooms with a pinch of salt into skillet. Increase heat to high; cook, stirring mushrooms occasionally, until mushrooms shrink slightly, about 5 minutes.
Transfer skillet to the oven and cook through, 15 to 20 minutes. Interior temperature should be at least 165 F (74 C). Transfer only the chicken breasts to a plate and loosely tent with foil; set aside.
Set skillet on the stovetop over medium-high heat; cook and stir mushrooms until brown bits start to form on the bottom of the pan, about 5 minutes. Pour water into the skillet, and bring to a boil while scraping the browned bits off of the bottom of the pan. Cook until water is reduced by half, about 2 minutes. Remove from heat.
Stir in any accumulated juices from the chicken into the skillet. Stir butter into mushroom mixture, stirring constantly until butter is completely melted and incorporated.
Season with salt and pepper. Spoon mushroom sauce over chicken and serve.