Preheat oven to 350°F (175°C). Line a 9×13 inch baking pan with parchment paper or lightly grease it.

In a medium saucepan, melt the butter over medium heat. Remove from heat.

In a large bowl, whisk together sugar and cocoa powder. Add melted butter and stir until combined.

Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.

In another bowl, mix flour, salt, and baking powder. Gradually add to the wet ingredients, mixing until just combined.

Fold in the chocolate chips.

Pour batter into the prepared pan, spreading evenly. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out mostly clean.

Melt white chocolate chips in a microwave-safe bowl in 30-second intervals, stirring in between until smooth. Use a piping bag or a ziplock bag with a corner snipped off to draw circles on top of the baked brownie. Use a toothpick to draw lines from the center to the edges of the brownie to create a spiderweb effect.

Place fondant or gummy spiders on top of the brownies for an extra spooky touch.