Melt butter and brown sugar together in a medium saucepan, bring to a boil while stirring constantly stirring until thick & bubbly. Pour into a greased 9 X 13 pan and spread evenly. Crumble toasted pecans over caramel and place sliced apples over pecans. Place sliced bread into pan. Beat eggs and milk together with vanilla and pour over bread. Cover and refrigerate overnight. Bake at 350 degrees for 45 to 50 minutes until golden & bubbly. Enjoy!