To peel the pearl onions, bring a pot of water to a boil, trim off the roots, then add into the boiling water. Leave the onions in the water for 2-3 minutes, just until the water starts to boil again. Transfer the pearl onions to an ice bath then gently squeeze to pop the onion out of the skin.
Preheat the oven to 375°F. Place a large, oven-proof skillet over high heat. Add the bacon and sear on both sides until crispy, about 5-6 minutes. Remove the bacon from the pan onto a plate lined with a paper towel. Keep the grease in the skillet.
Add two tablespoons of butter to the bacon grease. Place the chicken breasts, skin side down, in the hot grease and sear for 3-4 minutes, until the skin is crisping up. Flip over and sear the other side for 2-3 minutes (the chicken will NOT be cooked through) and place on a separate plate. Keep the drippings in the skillet.
Cook the pearl onions in the pan drippings until they are tender and beginning to brown. Toss in the chopped mushrooms and sliced onion and cook until they have released their moisture and are a consistent brown color throughout. Add the minced black garlic.
Sprinkle the flour over the vegetables. Stir so that all the veggies are covered. Season with salt and pepper, then pour in the chicken broth. Bring to a rolling boil.
Pour in the red wine and stir in the tomato paste, bay leaves, and thyme. Return to a rolling boil for about 10 minutes. Reduce the heat and continue to simmer for another 15-20 minutes, until the sauce is reduced by half.
Return the seared chicken to the skillet and spoon a bit of sauce on top of each. Place the oven-proof skillet in the oven and bake for about 20-25 minutes, or until the chicken's internal temperature reaches 165°F.
Remove the skillet from the oven. Ladle the sauce onto shallow dishes and place the chicken on top. Season with salt and pepper and garnish with fresh parsley, as desired. Serve alongside crusty French bread and enjoy!