Pat dry chicken thighs, season with salt and pepper.
Heat a large nonstick skillet over medium heat. Add the sliced mushrooms and sauté until they have released all of their water and are starting to brown, up to 10 minutes. Set aside.
Heat a skillet over medium high heat. Add 2 tablespoons of olive oil. When oil is hot, add the chicken thighs and allow to sear, undisturbed for about 5 minutes. When chicken easily releases from pan, flip and cook 5 minutes more. Cook until chicken is cooked through. Remove from pan.
Wipe out pan and return it to medium heat. Add the butter. When melted, add the onion, season with salt and pepper. Cook until softened and starting to turn golden, about 5-8 minutes.
Add the garlic and cook for 30 seconds, being careful not to burn.
Add the mushrooms and 1 tablespoon of thyme, then add the chicken broth and wine. Stir and scrape up the browned bits from the bottom of the pan.
Bring to a simmer and simmer 2-3 minutes.
Add the chicken and cook for about 2 more minutes, or until sauce has reduced.
Finish with the remaining tablespoon of thyme and season with more salt and pepper if desired.