Preheat your oven to 400°F (200°C).
Line a baking sheet with parchment paper.
Lay the saltine crackers in a single layer on the prepared baking sheet.
In a medium saucepan over medium heat, combine the butter and dark brown sugar. Stir continuously until the mixture comes to a boil. Allow it to boil for 3 minutes without stirring.
Pour the toffee mixture evenly over the arranged saltine crackers.
Bake for 5-7 minutes, or until the toffee is bubbly and golden brown.
Remove the baking sheet from the oven and immediately sprinkle the chocolate chips over the hot toffee. Let sit for a couple of minutes to soften.
Once softened, spread the melted chocolate evenly over the toffee layer.
While the chocolate is still warm, sprinkle the mini M&Ms on top.
Allow the toffee to cool at room temperature, then refrigerate for at least 1 hour to set completely.
Once set, break it into pieces and enjoy!
