In a saute pan, heat 1 tablespoon of butter. When the butter is melted, add the apples, shallots, garlic, and mint. Saute for 2 minutes. Add the couscous and olive oil and saute for 1 minute. Stir in the stock and bring to a boil, stirring for 2 minutes. Reduce the heat and cook for 1 minute. Stir in the remaining butter and remove from the heat. Cover and allow to sit for 2 minutes. Uncover and fluff with a fork. Fold in the feta cheese. Season with salt and pepper. Mound the couscous in the center of the platter. Lay the carved lamb over the couscous. Garnish with fresh rosemary and mint.