Preheat oven to 350 degrees Fahrenheit, line a 9"x13" cake pan with foil, allowing it to come over the edges, then coat foil with nonstick cooking spray.

For the brownies, in a large microwave-safe bowl, melt butter and chocolate chips together in 30 second increments, stirring between.  Stir mixture until smooth.

Quickly whisk in (by hand) brown sugar, white sugar, vanilla, eggs, and milk, just until incorporated (don't over-mix or brownies will be tough and lose their nice texture).

In a separate bowl, stir together flour, baking cocoa, baking powder, salt and corn starch. Add to chocolate mixture and stir just until incorporated (again, don't over-mix!).  

Pour and spread mixture into prepared pan and bake for approximately 16 minutes, or just until a toothpick comes out mostly clean, with a few moist crumbs on it. You don't want the toothpick to come out super gooey or completely clean, but moist crumbs are what you're shooting for.  Don't over bake or they'll lose their fudgy texture.

Let brownies cool in pan on a cooling rack for 20 minutes, then place in the fridge while you make the ganache.

For the ganache, melt butter with the chocolate chips in the microwave in 30 second increments, stirring between.  

Whisk in milk until smooth.  

Pour and spread over brownies, then sprinkle with Rainbow Crunch Mini Chocolate Chips.  

Put back in the fridge until ganache is set and brownies are cooled through.  

Lift foil from pan, slice into squares and enjoy!