Preheat the oven to 300 degrees.
Cook bacon in a large Dutch oven over medium heat until crisp and remove from pan. Save bacon for later use in a container. Reserve the drippings left behind in the pan.
Sprinkle ¾ teaspoon salt and ½ teaspoon pepper evenly over the chicken. Place 2/3 cup all-purpose flour in a shallow dish and dredge chicken it it. Shake off excess flour.
Pour 1 tablespoon oil to the bacon drippings left in the pan and swirl to mix over medium-high heat.
Place half of the chicken in the pan and cook for 5 minutes or until browned. Cook chicken on the other side for 2 more minutes and remove from pan. Repeat the same process with the rest of the oil and chicken.
Cook potatoes in the pan for 3 minutes or until browned, stir occasionally. Cook mushrooms in the pan for 3 minutes with ¼ salt, stirring occasionally.
Mix in brandy and cook until liquid almost evaporates (30 seconds or so) stirring occasionally.
Add chicken, shallots and stock to the pan and bring to boil.
Place peppercorns, thyme sprigs, bay leaf, ½ bunch fresh-leaf parsley in a double layer of cheesecloth and gather into a bundle with a butcher's twine. Put bundle in the pan and bake uncovered for 15 minutes at 300 degrees.
Scrub carrots clean and cut off tops to 1 inch. Add carrots to pan and bake for another 45 minutes or until vegetables are tender and chicken is cooked.
Discard herb bundle and remove chicken and vegetables from pan and keep warm.
Place pan over medium high heat, pour in champagne and bring to a boil. Scrape browned bits in pan and cook until mixture reduces to 2/3 cup (about 11 minutes).
Melt butter in a saucepan over medium high heat. Cook butter for 3 minutes or until browned, shaking pan occasionally.
Mix in 1 teaspoon flour and cook for 1 minute stirring with a whisk.
Gradually stir in butter mixture to the reduced Champagne mixture stirring with a whisk. Let cook for 1 minute or until slightly thickened.
Stir in ¼ teaspoon salt and ¼ tsp black pepper.
Serve sauce with chicken and vegetables garnished with chopped fresh parsley and thyme.