You know that junk drawer that you toss everything into? Come on — admit it. Everyone has one in their house. Well, this is the dessert version of that. Toss whatever leftover Halloween candies your heart desires into these brownies. It'll be delicious.
Put the eggs and sugar in the bowl of an electric mixer with the paddle attachment and beat at medium-high speed for 20 minutes. In a small pot, heat the butter until almost boiling, and slowly drizzle into the egg mixture.
Preheat the oven to 350 degrees.
Take a little of the egg mixture and mix into the cocoa powder in a separate bowl to avoid lumps and add back into the egg mixture. Add the salt, baking powder, and vanilla extract. Fold in the flour and then candy pieces. Grease a 9-by-13-inch baking dish and transfer the mixture to the baking dish. Bake for 30 minutes.