Steps
1. Preheat the oven to 350°F (175°C) and line a square baking pan with parchment paper.
2. In a microwave-safe bowl, melt the butter. Add the sugar and mix well.
3. Beat in the eggs one at a time, followed by the vanilla extract.
4. In a separate bowl, whisk together the flour, cocoa powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined.
5. Fold in the dark chocolate chips, milk chocolate chips, and white chocolate chips.
6. Pour the batter into the prepared baking pan and spread it evenly.
7. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
8. Allow the brownie to cool completely before cutting into squares and serving.