01 - Boil cider in a large heavy saucepan until reduced to half a cup, checking volume carefully. Reduce heat before adding the remaining caramel-base ingredients.
02 - Add sugar, butter, salt, cream, corn syrup and baking soda cautiously. Bring to a controlled boil with ample headroom; reduce heat immediately if foam climbs the pan.
03 - Stir and watch closely, beginning checks around seven minutes. Look for a caramel-colored sauce that coats a spoon after a small sample cools; do not taste directly from the pan.
04 - Remove from heat before adding vanilla and spice. Cool until safe to transfer, then refrigerate in a clean heat-safe container. This is a refrigerated sauce, not a shelf-stable canning recipe.