Combine brown sugar, peanut butter, honey and butter in a medium saucepan over medium-low heat, stirring frequently.
Bring sugar mixture just to a boil and then continue cooking for an additional 2-3 minutes stirring constantly, or until sugar dissolves.
Stir in oats and crispy rice cereal until evenly coated.
Let mixture cool for 5 minutes.
(Optional) Meanwhile, pick out a handful of M&Ms from the trail mix and set aside.
Place parchment paper in an 8x8 inch baking dish. Make sure the paper hangs over on either side so you can pull out the granola bars and cut them up with ease.
Once mixture has cooled slightly, fold in trail mix and press into the prepared dish.
Sprinkle M&Ms and chocolate chips over the top of the bars and use the bottom of a bowl or cup to press them into the bars. You don't want them to fall out when cutting!
Place dish into refrigerator and let bars set up for 1-2 hours.
Cut into bars and serve!