Preheat your oven to 325F

Line a baking tray or casserole dish with parchment paper and lay down a single layer of the saltine crackers. You may need to break a few to fill in gaps.

Place the butter and brown sugar in a small saucepan and bring to a boil over medium heat. Allow the mixture to melt and blend completely before removing from heat. (You can stir it but it won't burn if you don't.)

Immediately pour the melted caramel over the crackers in an even layer.

Place the crackers in the oven for 10 minutes, until the caramel is completely absorbed and the crackers have taken on a glossy, hard caramel appearance.

Sprinkle the chocolate chips over the hot crackers and let melt. Spread with an offset spatula and immediately sprinkle on M&Ms to allow them to stick to the chocolate.

Place in fridge and let set.