Step 1

Start by spraying an 8x8-inch square baking pan thoroughly with non-stick cooking spray. Then, grease a large mixing bowl and large cooking pot.

Step 2

Add the crispy rice cereal and one cup of mini marshmallows to the greased mixing bowl, and set aside.

Step 3

Slice the butter into chunks and add it to the cooking pot over low heat, stirring consistently until the butter is melted.

Step 4

Add the remaining 5 cups of mini marshmallows to the cooking pot. Stir them with the butter on low-medium heat until the marshmallows are completely dissolved and a creamy mixture forms. Be careful the heat is not too high, or you can burn the marshmallows and get a sticky mess.

Step 5

Stir the vanilla extract into the creamy marshmallow mixture until evenly combined. Then, remove from the heat.

Step 6

Pour the marshmallow mixture over the rice cereal in the separate mixing bowl. Use a rubber spatula or wooden spoon to fold the ingredients together. If it is too sticky and hard to mix, you can use your hands - just grease them first.

Step 7

Gently fold in the chocolate M&Ms until they are evenly incorporated.

Step 8

Transfer the mixture into the greased baking pan and press it gently into the edges and corners of the pan. Be careful not to press too firmly, or the rice crispy treats can become hard and tough instead of gooey and chewy.

Step 9

Press additional M&Ms into the top of the rice krispie treats if desired. Cut into squares and enjoy!