Smoked Duck Sandwich

Name: Smoked Duck Sandwich
Ingredients: Two 2/3-pound duck breasts (see Cook's Note); 1 tablespoon curing salt; 1 teaspoon ground coriander seeds; 1 teaspoon ground dill seeds; 1 teaspoon garlic powder; 1 teaspoon ground juniper berries; 1 teaspoon ground pepper; 1/3 pound smoked bacon; 1/2 onion; 2 tablespoons butter; 1/2 cup white wine; 1/2 cup chicken stock (or duck stock if available); 1 small savoy cabbage, chopped into 1/4-inch dice; Salt and pepper; Mayonnaise, for serving; 4 white buns of your choice