Line an 11×7 inch pan with foil. Spray with non stick spray.
In a large bowl, melt butter in the microwave for 1-2 minutes, or melt in a small pot over low heat and then transfer to the bowl.
Whisk in the sugars, eggs, milk, and vanilla. Then whisk in the cocoa powder until the batter is smooth and not lumpy.
Add flour gradually, stirring until everything’s evenly combined.
Pour the batter out into the prepared pan, and use a spatula to gently spread it out evenly. Bake at 350 degrees for 25-30 minutes or until a toothpick inserted in the center comes out clean. Allow it to cool completely.
Heat the heavy cream in a medium sauce pan over medium-medium low heat. Add in the chocolate chips, stirring occasionally until they’ve both completely incorporated and the ganache is smooth.
Pour the ganache over the completely cooled brownies. Smooth it out with an offset spatula.
Sprinkle the M&Ms, or rainbow chocolate chip candies, over the top of the ganache. Refrigerate until the ganache has set. Cut brownies into squares to serve and enjoy!