Ingredients: , 2.5 tablespoons unsalted butter, 1 large shallot finely chopped, 1 bottle tawny port (750 ml or 3 1/4 cups), 3 sprigs fresh thyme, 2.5 cups chicken broth, 1 oz. dried porcini mushrooms, 2 tablespoons all-purpose flour, 1 teaspoon balsamic vinegar, 1 sea salt, 1 freshly ground pepper...