Braised Chicken Legs with Cheesy Polenta and Sauteed Greens

Name: Braised Chicken Legs with Cheesy Polenta and Sauteed Greens
Ingredients: 2 lemons, sliced 1/2-inch thick; 2 medium yellow onions, sliced 1/2-inch thick; 6 chicken leg quarters; 1 teaspoon dried oregano; 1 1/2 teaspoons salt; 1 1/2 teaspoons ground black pepper; 1/4 cup olive oil; 2 cups chicken stock, preferably homemade; 2 cups dry white wine; 3 cups whole milk; 1 cup polenta (not quick-cooking); 1 cup grated white Cheddar; 1 tablespoon red wine vinegar; 8 ounces sauteeing greens, such as kale, beet greens or chard, hand-torn into 3- to 4-inch pieces