Heat a large pan over medium-high heat. Sear the chicken until golden brown, about 4 minutes per side. Add the diced onion, minced garlic, and sliced mushrooms. Season with salt and pepper. Cook for 3-4 minutes until the onions are translucent. Deglaze the pan with the red wine and add a handful of fresh thyme stalks. Transfer the chicken to a warm oven preheated to 100°C (212°F) while you finish the sauce.
Let the wine sauce reduce over medium heat for about 5 minutes. Add the bay leaves. Remove the pan from heat and stir in the crème fraîche. Season to taste with salt and pepper. Return the chicken to the sauce and ensure it has reached an internal temperature of 74°C (165°F) before serving.