For the Rice Krispies Treats:

Cup of Yum
1. Cover bottom and sides of a 9" x 9" baking pan with wax paper. Spray with non-stick cooking spray and set aside.
2. Melt butter in saucepan over medium heat. Once butter is liquid, add mini marshmallows and stir until melted.
3. Remove pan from heat and mix in Rice Krispies cereal until all cereal is coated in marshmallow mixture.
4. Scoop Rice Krispie treat "batter" into baking pan. Cover with a sheet of wax paper and press down to form to the shape of the pan.
5. Chill covered Rice Krispie treats in fridge until fully cooled. (Around 15-30 minutes).

For the LEGO topping:

1. Combine all ingredients (except the gel colors and M&M's) in a stand mixer and mix on medium speed until well combined and smooth. 
2. Split icing evenly into 3 small mixing bowls. Add a couple drops of gel food coloring to each bowl (one color per bowl) and stir. Continue adding gel color drop by drop until your icing is the desired shade.

Put it all together:

1. Cut Rice Krispies treats into small rectangles. Dip the top of each individual treat into one color icing.
2. Set on a baking sheet and place 6 M&Ms in the same color of the icing on top of each treat to look like a Lego block.
3. Allow to set for an hour until icing hardens.