Braised Chicken with Sweet Onions and Parmigiano

Name: Braised Chicken with Sweet Onions and Parmigiano
Ingredients: 16 chicken thighs, bone in and skin on; Salt and freshly ground black pepper; 8 ounces pancetta, cut into ¼-inch cubes; 4 leeks, white and pale green parts only, sliced into ¼-inch-thick rounds, rinsed thoroughly, and drained; 10 medium red onions, halved and sliced into thin half-rounds; 8 cups chicken stock; ¼ cup all-purpose flour; 1 cup dry red wine, such as Sangiovese di Romagna; 1 cup whole milk; 8 slices Tuscan or other country bread; ¼ cup extra virgin olive oil; 1 cup freshly grated Parmigiano-Reggiano