Preheat your oven to 350°F (175°C).
Grease and line an 8x8-inch baking pan with parchment paper.
In a saucepan over medium heat, melt the butter. Once melted, remove it from heat and stir in the sugar until combined.
Allow the mixture to cool for a few minutes, then whisk in the eggs and vanilla extract until smooth.
In a separate bowl, combine cocoa powder, flour, salt, and baking powder.
Gradually stir the dry mixture into the wet mixture until just combined. Be careful not to overmix.
Fold in the chocolate chips.
Pour the brownie batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for about 25 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.
Once baked, remove from the oven and allow to cool completely in the pan on a wire rack.
Once cooled, spread a layer of chocolate frosting over the top of the brownies.
Sprinkle the rainbow candy-coated chocolates on top of the frosted brownies for a festive touch.
Cut into 12 squares and serve.