Preheat oven to 400 degrees.
Line a rimmed cookie sheet or jelly roll pan with aluminum foil or parchment paper and spray generously with cooking spray.
Place your saltines on your cookie sheet in a single layer. (How many saltines you use will depend on the size of your pan. I usually use around 45 – it’s OK if there is a little space around the edges, just pull up the foil to the edges of the crackers to help keep that toffee on the top!)
In a saucepan, bring your butter and brown sugar to a low boil over medium high heat and then stir continuously for 4-5 minutes.
Remove from heat and immediately stir in your vanilla extract.
Pour the hot mixture over your crackers, spread evenly and bake for 5 minutes until it’s bubbling all over.
Remove from oven, sprinkle your chocolate chips immediately on top of the crackers, let them sit and soften for a few minutes, then spread chocolate evenly on top of crackers.
Sprinkle with nuts, sprinkles, M&M’s or any other toppings you like.
Let cool completely, then move to the refrigerator to cool. After a couple of hours, remove from the foil or parchment paper and break up into bite size pieces.