Preheat oven to 350 degrees. Spread pecans in a shallow baking pan and bake until golden, about 8-10 minutes, stirring occasionally.
Meanwhile, place bread cubes in a greased 3 quart or larger slow cooker. Peel, core and thinly slice the apples. Mix lightly together the sugar, cinnamon and nutmeg, add eggs and mix well. Blend in half and half or milk and then stir in bourbon or brandy.
Lightly mix pecans with bread and apples. Pour egg mixture over bread. Drizzle with butter. Cover and cook on low until apples are tender when pierced and custard is set, about 3 1/2 to 4 1/2 hours.
Let pudding stand, covered, for about 15 minutes. Serve warm with ice cream, if desired.