Tender Pork Sandwiches with Blueberry Glaze

Name: Tender Pork Sandwiches with Blueberry Glaze
Ingredients: 1 (2.5-3 lb.) pork tenderloin; 1 teaspoon dried oregano, crushed; 1 teaspoon salt, divided; ½ teaspoon garlic powder; ½ teaspoon dried basil, crushed; ½ teaspoon ground black pepper; 1 cup seedless raspberry preserves; 1 cup fresh or frozen blueberries; ¼ cup finely chopped shallots (2 medium); ¼ cup balsamic vinegar; 1 clove garlic, minced; 1 tablespoon olive oil; 2 tablespoons cornstarch; 2 tablespoons cold water; 6 sandwich buns, split and toasted