Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan or line it with parchment paper.

Melt the Butter and Mix Wet Ingredients: In a large microwave-safe bowl, melt the butter. Once melted, stir in the granulated sugar until well combined. Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.

Combine Dry Ingredients: In a separate bowl, sift together the all-purpose flour, unsweetened cocoa powder, baking powder, and salt.

Mix Wet and Dry Ingredients: Gradually add the dry ingredients to the wet mixture, stirring just until combined. Fold in the semi-sweet chocolate chips.

Bake the Brownies: Pour the batter into the prepared baking pan and spread it evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with only a few moist crumbs attached.

Create the Spiderweb Decoration:

While the brownies are baking, melt the white chocolate chips in a microwave-safe bowl in 30-second intervals, stirring after each, until smooth.

Let the brownies cool slightly. Transfer the melted white chocolate into a small piping bag or a ziplock bag with a tiny corner snipped off.

Draw concentric circles onto the brownies, starting from the center and working your way out to the edges.

Drag a toothpick from the center to the edge of the brownies to create a spiderweb effect.

Cool and Serve: Allow the brownies to cool completely before cutting them into squares. Enjoy your spooky Halloween treat!