Place one paper bag inside the other and pour cereal, peanuts, and M&M candies into it.
Add brown sugar, butter, Karo syrup and salt to a large saucepan. Boil for 1-1/2 minutes. Remove from heat and stir in the baking soda. Be careful because the mixture will foam up and be very hot. Pour into the paper bag over the cereal mixture.
Roll the top of the bag down and shake to distribute the sugar mixture throughout the cereal mixture. Heat bag in the microwave on high for 1 minute. Remove and reshake. Return to the microwave for a total of 3 times.
Spread out on rimmed cookie sheets to dry for a couple hours or overnight. Occasionally break up the mix. Store dried mix in an airtight container.
Notes
Alternately, this mix can be made in a large microwave-safe bowl.
This recipe was calculated using the exact brands and measurements I used to make this recipe. If you are following a strict diet please note changing anything will cause the nutritional info to change. My calculations are intended as a guide only.