1. Heat a grill or grill pan to medium-high.
2. Place the apples in the grill pan and cook the apples for 2 minutes on each side, allowing for a quarter turn on each side. Reserve on a warm plate until needed.
3. Heat a large skillet over medium-high heat. Season the foie gras evenly with the salt, white pepper, and sugar. Sear the foie gras for 30 seconds on each side to achieve a golden brown color. Reserve the foie gras on the plate with the apples.
4. Add the applejack to the hot pan and let it reduce to 1 tablespoon. Add the veal stock and reduce by half. Whisk in the cold butter. Place the grilled apples on a plate. Place a small bunch of watercress in the center of each apple ring. Place a portion of foie gras leaning against the watercress and drizzle with the sauce.
5. Garnish each plate with 1 tablespoon of the candied nuts.