Season the chicken all over with salt and pepper. Heat the olive oil In a large soup pot over medium heat. When the oil shimmers, add the chicken and sear until golden brown on both sides, about 5 minutes per side. Toss in the shallots and cook another 3-5 minutes. Add the celery, carrots, and thyme. Season with salt and pepper. Cook another 5 minutes. Pour in the chicken broth and bring to a boil over high heat. Cover and cook for 15-20 minutes or until the chicken is cooked through.Meanwhile, make the dumplings. In a medium bowl, whisk together the flour, baking powder, sage, and a pinch each of salt and pepper. Add the buttermilk and cheese and mix until just combined.Remove the chicken from the soup and shred using 2 forks, discard the bones and skin. Set aside.Bring the soup to a boil over medium-high heat. Drop a heaping tablespoon of the dough into the soup, adding about 6 dumplings to the soup at a time. Cover, and cook for about 8-10  minutes, until the dumplings are cooked through and puffy. Carefully move the dumplings aside and slide the shredded chicken into the soup. Season to taste with salt and pepper. Divide the soup and dumplings between bowls and serve topped with pepper. Enjoy!