Pork Braised In Champagne Vinegar

Name: Pork Braised In Champagne Vinegar
Ingredients: One 3 1/2-pound fresh picnic pork shoulder with skin; 3 garlic cloves, thinly sliced; Salt and freshly ground pepper; 1/4 cup extra-virgin olive oil; 2 cups thinly sliced shallots; 1 teaspoon ground cumin; 1 teaspoon ground coriander; 1 teaspoon powdered mustard; 3/4 cup Champagne vinegar; 2 cups dry sparkling wine; 2 cups chicken stock; 2 large sage sprigs; 1 pound red grapes, stemmed; 2 tablespoons unsalted butter; 2 tablespoons chopped flat-leaf parsley; 2 tablespoons snipped chives