Step 1: Prepare the Pan: Line a baking sheet with parchment paper. Set aside for pouring melted chocolate.

Step 2: Melt the Dark Chocolate: Place dark chocolate in a microwave-safe bowl. Microwave in 20-second intervals, stirring each time until smooth. Pour melted chocolate onto the prepared baking sheet and spread into a thin, even layer using an offset spatula.

Step 3: Melt the White Chocolate: In a separate bowl, melt the white chocolate using the microwave or double boiler method. Transfer melted white chocolate to a small piping bag or resealable plastic bag and snip a tiny corner for precision.

Step 4: Create the Spider Web: Pipe concentric circles of white chocolate over the dark chocolate layer. Using a toothpick or skewer, drag lines from the center to the edges of the chocolate to create a spider web effect. Optionally, add candy spiders, sprinkles, or other decorations before the chocolate sets.

Step 5: Set the Chocolate: Allow the chocolate to cool at room temperature for 15–20 minutes, or refrigerate for 15 minutes until firm. Break or cut into pieces for serving.