BREAD PUDDING: Preheat the oven to 350 degrees F. Lightly grease or spray a 9x13" baking dish.
in a large bowl, toss together the bread cubes and the apple pieces. Transfer to the baking dish. In the same large bowl, whisk together the remaining ingredients except for the butter. When combined, continue to whisk while pouring over the bread/apple mixture (just to make sure the spices are evenly distributed).
Gently combine the bread and egg mixture, making sure each piece of bread is soaking in part of the egg and milk mixture. Allow to stand for at least 15 minutes (you can do this the night before, cover it tightly, and then bake in the morning).
When the egg/milk mixture has mostly soaked into the bread, dab the butter over the bread and place the baking dish in the preheated oven and bake for 40-50 minutes or until the center is set but not dry or burned. Remove from the oven and allow to stand for 5 minutes.
Cut into pieces and serve with warm Buttermilk Syrup (and vanilla ice cream if you so desire).
BUTTERMILK SYRUP: Combine buttermilk, sugar, butter, corn syrup, and baking soda in a LARGE pot, like one you would use to make soup. You need more pot than ingredients because this will boil all over the stove if the pan is too small.
Bring ingredients to a boil and reduce heat to low (as long as it's still bubbling, you're okay). Cook, stirring frequently, for 8-9 minutes. You're basically making candy here and candy-making requires constant vigilance.
When it's done, it should take on this luscious golden-brown color. Remove from heat and add vanilla.
There will be foam on top. It tastes good, but not really pretty. If you prefer, you can skim it off, otherwise, just give it a stir.