Preheat oven to 350°F/175°C. Lightly grease a 9x13 baking dish, set aside.
In the bowl or a stand mixer, beat melted butter, sugars and vanilla until light and fluffy, about 2 minutes. Add eggs, one at a time, mixing until mixed.
In a medium size mixing bowl whisk together flour, cocoa powder, baking powder, cornstarch, and salt. With mixing speed on low, alternate adding dry ingredients and milk. Mix just until combined.
Remove bowl from stand and pour batter into prepared pan. The batter will be thick, so using a rubber spatula, spread into an even layer. Place in oven and bake for 18-25 minutes. The brownies will be done, so do not over-bake or you will have dry brownies! Remove from oven and allow to cool in the pan.
Meanwhile to prepare the ganache, in a 2 cup glass measuring cup, combine chocolate chips and heavy cream. Microwave for one minute, stir, then repeat. Stir chocolate until all of the chips are melted and it becomes smooth. Beat for 1 minute and then pour over the top of the brownies. Spread evenly and sprinkle with desired toppings. Serve warm or cold.