Cut breasts into 2 or 3 pieces depending on size. Salt and pepper chicken and shake them in a zipped plastic bag with the flour. In a large saute pan melt the butter and add the oil. Take the chicken pieces from the bag and gently shake off excess flour. Brown the chicken pieces on each side in batches. Place them in a large braising pot or Dutch oven. Deglaze the pan with a cup of chicken broth and pour into the pot along with the rest of chicken stock, tomato paste (I mix this with some broth to loosen it up), red wine, carrots, celery, thyme, garlic and bay leaves. Add in more wine or chicken broth to just about cover the chicken if needed. Place a lid on top and refrigerate overnight.

The next day, preheat the oven to 325F. Place the pot of chicken in and braise for 2 1/2 to 3 1/2 hours or until the chicken is tender but still staying on the bone. Stir occasionally.

For the pearl onions, cut off the root end and cut an "X" with your knife in the bottom. Bring 2 cups of water to a boil and add onions, boil for 1 min. You can then peel the skin off the onions easier or just pop them out of their skins. Set aside.

Meanwhile, cook the bacon in a medium saute pan until done but not too crisp, remove and drain on a paper towel lined plate. Drain off but 2 Tbsp. of bacon fat. In the fat, fry the pearl onions until golden and cooked through. Season with salt and pepper and remove to a bowl. In the same pan add the 1 Tbsp. butter and saute the mushrooms until they have given up their liquid and are nicely browned. Store the bacon, mushrooms and onions together in a covered bowl and refrigerate.

Once the chicken is done, remove it and strain the sauce. Discard the carrots, onion, celery etc. Place the sauce in a saucepan and reduce on medium heat by 1/3, this will take about 20 to 45 min. depending on how much liquid you have. With a wire whisk, add in the butter and flour mixture, small amounts at a time (1 Tbsp.) and continue to whisk until desired thickness. You don't want it to be as thick as a gravy but still more like a sauce. Add in the pearl onions, bacon, mushrooms and chicken. Let cool and refrigerate overnight for best flavors or serve over mashed potatoes or egg noodles.