Preheat oven to 325 degrees. Line a 17.25x11.5x1 jelly roll pan with tin foil. Spray with cooking spray.
Line the jelly roll pan with all 46 crackers.
In a medium saucepan, add in butter and brown sugar. Melt the butter over medium heat.
Once the butter is melted, watch for the brown sugar to bubble around the edges. Let the mixture boil for three minutes while stirring. It will be thick and foamy as it bubbles.
Remove mixture from the heat and pour over top of the saltine crackers. Spread the brown sugar mixture with a butter knife to cover all the crackers.
Place the saltine crackers in the 325 degree oven for 8 minutes. This will spread the toffee evenly on all the crackers.
Remove from the oven and let cool. Break the saltines apart. If you want the crackers to be a little neater, while the toffee is still hot, move the crackers to a cooling rack that has a piece of parchment paper under it to catch the toffee drippings.