Foie Gras with Pineapple and Pistachios

Name: Foie Gras with Pineapple and Pistachios
Ingredients: 2 tbsp. butter; 1 ripe pineapple, peeled, cored, and diced; 1⁄2 cup sugar; 1⁄2 cup rice wine vinegar; 1⁄2 cup pineapple juice; 2 tbsp. roasted pistachios, shelled, chopped, and toasted; 1 1⁄2 lb. fresh whole foie gras, sliced into 16 ½-thick pieces; Salt and freshly ground black pepper; 8 tbsp. balsamic vinegar; 8 sprigs chervil