Place halved chicken in a stockpot along with carrots, onion, celery and garlic. Add 2 1/2 quarts cold water. Bring to a low boil, reduce to simmer and cook until chicken is tender, but not falling apart, approximately 30-40 minutes. Once chicken is tender, strain and reserve 2 quarts of de-fatted stock and cool chicken, skin and debone. Place stock and deboned meat on the side for later use. In a dutch oven, heat oil over medium-high heat. Add flour and, using a wire whisk, stir until dark brown roux is achieved. Add onions, celery, bell peppers and garlic. Sauté 3-5 minutes or until vegetables are wilted. Add Rotel tomatoes, basil, thyme and hot chicken stock, 1 cup at a time, until a slightly thickened stew is achieved. Add bay leaf, mushrooms and half of the green onions. Bring to a rolling boil, reduce to simmer and cook 30 minutes. While sauce is cooking, preheat oven to 350 degrees F. After sauce has cooked 30 minutes, add chicken and season to taste using salt and pepper. Additional stock or water may be necessary to retain stew-like consistency. Add remaining green onions, parsley and adjust seasonings if necessary. When ready to serve, heat biscuits thoroughly in oven and, when hot, split in half. Place the bottom half in the center of a 10-inch plate and top with a generous portion of the chicken fricassee. Top with the remaining biscuit half. Garnish with parsley.