Preheat the oven to 350F. Prep a 9-inch square baking dish by putting a sheet of parchment paper over the bottom and sides. Spray with non-stick spray.
Halfway fill a medium pot with water and heat over medium heat until simmering. Place a smaller pot on top of the first to create a double broiler.
Add to the smaller pot ½ cup of chocolate chips and the butter. Use a spatula or wooden spoon to stir constantly as the chocolate melts.
Make sure the chocolate and butter are well combined.
Remove the smaller pot from heat and set aside to cool slightly.
In the bowl of a stand mixer, whisk together the eggs, sugar, and vanilla on high speed.
You can also use a handheld electric mixer or word really hard with your arms. Whip for about 5 minutes or until light and fluffy.
Turn the mixer to low and carefully pour in the melted chocolate and butter mixture. Whisk just until combined. You may need to use a spatula to scrape down the sides of the bowl.
In a new bowl, add the flour, cocoa powder, baking powder, and salt. Whisk to combine.
Slowly add the dry ingredients to the stand mixer and whisk until combined. Avoid overmixing.
Roughly chop the maraschino cherries and add to the bowl of the stand mixer. Mix to combine.
Add the remaining chocolate chips and mix briefly to combine. Make sure to scrape the sides and bottom of the bowl so every little bit gets mixed in.
Pour the batter into the previously prepared baking dish and spread evenly with a spatula.
Put in the oven and cook for 25-30 minutes or until a toothpick can be inserted and come out clean.
Once cooked, take out of the oven and let cool in the pan. You can then use the edges of the parchment paper to lift it out of the pan and onto a wire cooling rack.
While waiting for the brownies to fully cool, you can prepare the icing. In a small bowl, mix together the powdered sugar and juice from the maraschino cherries.
If the icing is too thick, add more juice or water. If too thin, add more powdered sugar.
Wait until the brownies are fully cooled then drizzle the icing on top.
Cut and serve.