Preheat oven to 400° F
Line a Jelly Roll pan with foil and grease with a liberal dose of cooking spray. If you prefer, you can also use a non-stick silicone baking mat.
Place the crackers in a single layer on the baking sheet.
In a medium saucepan, melt the butter and then fold in the brown sugar. Bring to a low boil for 3 minutes, stirring constantly so that it does not burn.
Stir in the vanilla extract
Layer the brown sugar mixture on top of the crackers. Use a spatulate to make sure all of the crackers have equal coating.
Place the base mixture in the oven and bake for 3-5 minutes, or until you can see the brown sugar mixture bubbling.
Gently remove the pan from the oven, add the chocolate chips on top, and then place the pan back in the oven for another 3 minutes to melt the chocolate.
Remove from the oven and use a spatulate to spread the chocolate evenly across the top of the cracker base.
Before the melted chocolate has a chance to cool, liberally sprinkle the white chocolate chips, red & green M&Ms, and Christmas sprinkles across the top.
Set aside and allow to cool, either on the kitchen counter or you can place it right into the refrigerator (although I find sometimes that cooling in the refrigerator causes the chocolate to form white spots).
Optional: Wait a few minutes then take a spoon to gently spread the softened white chocolate into little swirls.
Once it has fully cooled, you can cut into pieces and serve on a plate, or pack some away in gift boxes as a lovely DIY Christmas gift.