Place duck halves skin side up on sizzler or sheet tray and sprinkle with ground pepper. Place in preheated 375°F oven for 12-15 mins or until fat is rendered out and skin is crispy. Remove from oven and keep warm. Pour excess fat from pan and deglaze with wine. Add green peppercorns, mustard, demi glace. Adjust seasonings. Pour or spoon over duck halves. Serve immediately.