1. Preheat the oven to 350°F (175°C). Line an 8×8-inch (20×20 cm) baking pan with parchment paper, leaving some overhang for easy removal.

2. In a microwave-safe bowl or double boiler, melt the butter and chopped chocolate together until smooth. Let it cool slightly.

3. Whisk in the granulated sugar, brown sugar, eggs, and vanilla extract until shiny and smooth.

4. Sift in flour, cocoa powder, and salt. Fold gently with a spatula until just combined — do not overmix.

5. Pour the batter into the prepared pan and smooth the top.

6. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Let brownies cool completely in the pan.

7. Melt white chocolate chips (or candy melts) with 1 tablespoon of milk in the microwave in 15-second intervals, stirring until smooth.

8. Pour the melted chocolate into a piping bag or small zip-top bag and snip off the tip.

9. Spread a thin layer of chocolate ganache or frosting over the brownies (optional).

10. Pipe concentric circles of melted white chocolate on top.

11. Using a toothpick, drag lines outward from the center to the edges to form a web pattern.

12. Add candy spiders, plastic toppers, or draw tiny chocolate spiders for a spooky effect.

13. Let the topping set for about 15 minutes before cutting into squares.