Line the 8X8 pan with foil or parchment paper with an overhang on all sides, then coat with non-stick spray.
Arrange 16 crackers in a single layer on prepared pan and set aside.
Cook sugar and butter in a saucepan over low until sugar is dissolved and butter melted.
Add condensed milk, cream, corn syrup, and salt.
Increase heat to bring mixture to a gentle simmer. Stir constantly until mixture thickens and is a deep golden color, about 6 – 8 minutes.
Remove mixture from heat and stir in vanilla extract.
Pour 1/3 of the mixture on the crackers.
Place next 16 crackers on top of toffee.
Pour and spread toffee over this layer of crackers.
Repeat one more time, ending with toffee.
Heat chocolate chips in a microwave safe cup or bowl, stirring every 20 or 30 seconds until chocolate is melted.
Pour and gently spread over toffee layer.
Let cool for about 10 minutes.
If you are adding a topping, this is the time to sprinkle on chopped nuts, flaked salt, or sprinkles.