Preheat oven to 120C/250F.
Heat a tablespoon of olive oil in a large Dutch oven. (If you have a cast iron pot it's perfect for it.) Fry your bacon lardons for 8-10 minutes until browned and remove them to a plate lined with paper towel.
Season your chicken pieces with salt and pepper and brown them in the same pot in batches to avoid overcrowding. Remove to the same plate as bacon. You are not cooking your chicken all the way through, just browning on both sides.
Slice your onions and carrots in medium sized chunks and add them to the pot with salt and pepper, cook over medium heat for 10 minutes, add the garlic and cook for 1 minute longer stirring the whole time not allowing it to burn. Add your brandy and scrape all the burned bits to incorporate them into your sauce, now add bacon and chicken with all the juices they collected, pour in your wine, chicken stock and thyme sprigs and bring to a boil. Once boiling, cover with a lid and put it in the oven for 55 minutes.
When chicken is no longer pink mix melted butter with flour and stir in the sauce. Slice mushrooms thickly and add to the pot, taste and adjust the seasoning if needed. Put back in the oven with the lid off for 10-15 minutes to allow the sauce to thicken.