Apple Caramel Crumb Bars
You can make the caramel sauce ahead and refrigerate it for up to 2 days. Reheat in microwave on medium power until slightly warm. You can make the base ahead and let it stand at room temperature, 8 hours to overnight. You can make the filling, cover it tightly with plastic wrap, and refrigerate it, 8 hours to overnight. Bring to room temperature before using.
The whole pan can be stored, tightly covered, in the refrigerator for up to 2 days or frozen for up to 2 weeks. Cut into bars before serving.
Substitute brandy for the whiskey if preferred. Substitute cinnamon for the apple pie spice if preferred. Replace orange zest with lemon zest if preferred. Add 1 tablespoon orange zest to the filling if desired.