Trout in Riesling

Name: Trout in Riesling
Ingredients: 2 tablespoons (1 oz) unsalted butter plus additional for greasing; 1 medium carrot; 1 celery rib; 4 (6- to 8-oz) trout fillets with skin; 1 1/2 teaspoons salt; 1 teaspoon black pepper; 4 medium shallots, cut lengthwise into 1/8-inch-thick slices (1 cup); 2 fresh parsley sprigs; 5 black peppercorns; 1 1/2 cups water; 1 1/2 cups dry Riesling; 3/4 cup heavy cream; 2 teaspoons cornstarch; 2 teaspoons chopped fresh tarragon; 1/2 teaspoon fresh lemon juice; an adjustable-blade slicer; tweezers or needlenose pliers