Step 1: Prep the Pan

• Line a 9-by-13-inch baking dish with foil, leaving an inch or two of overhang on the sides.

• Spray the foil with nonstick cooking spray to prevent sticking.

Tip: Use enough foil to create a work surface for decorating later.

Step 2: Melt the Marshmallows

• Divide 1.5 bags of marshmallows (about 18 ounces) evenly between two large microwave-safe bowls (about 9 ounces per bowl).

• Add 3 tablespoons of butter to each bowl.

• Microwave one bowl for about 45 seconds until the marshmallows start to melt. Stir well, then microwave for another 30 seconds until completely melted.

• Add green gel food coloring to the first bowl and stir until vibrant and even.

• Repeat the melting process with the second bowl, tinting it with purple gel food coloring.

Tip: Stir in small amounts of food coloring at first—you can always add more for a bolder hue.

Step 3: Mix in the Cereal

• Add 4.5 cups of crispy rice cereal to the green marshmallow mixture and stir until fully coated.

• Repeat with the purple marshmallow mixture and the remaining 4.5 cups of cereal.

Tip: Work quickly while the marshmallows are warm to make mixing easier.

Step 4: Form the Layers

• Grease your hands with cooking spray or wear disposable gloves to prevent sticking.

• Using one hand for green and one for purple, scoop blobs of each color mixture into the prepared pan, randomly distributing them to create a mottled, layered effect.

• Once all the cereal is in the pan, press the mixture evenly to smooth the top.

Tip: Don’t overmix the colors in the pan to keep the green and purple swirls distinct.

Step 5: Cool and Cut

• Let the treats cool and set completely, at least 1 hour, at room temperature.

• Use the foil overhang to lift the treats from the pan. Peel back the foil edges to create a flat work surface.

• Trim the edges with a serrated knife for neat squares, if desired, and cut into 9 rectangles.

Tip: Separate the cut treats slightly on the foil to make decorating easier.

Step 6: Make the Marshmallow Web

• Place the remaining half bag of marshmallows (about 6 ounces) in a large microwave-safe bowl.

• Microwave for 45 seconds, stir, then microwave for another 30 seconds until fully melted. Let cool slightly until just warm to the touch.

• Wear disposable gloves, grab a handful of melted marshmallows, and rub between your hands. Pull your hands apart to create long, web-like strings.

• Drape the strings over the treats in different directions to form a spider web pattern, scooping more marshmallows as needed.

Tip: Work quickly—the marshmallow hardens fast. If it gets too stiff, microwave for 10 seconds to soften.

Step 7: Add the Spiders

• Melt 1/2 cup of semisweet chocolate chips in a double boiler or microwave at 50% power in 30-second intervals, stirring until smooth.

• Transfer the melted chocolate to a piping bag with a small, plain tip (or a zip-top bag with a tiny corner snipped off).

• Pipe 8 spider legs on each treat, forming a starburst shape.

• Place a halved chocolate-covered peanut or jellybean, cut side down, in the center of the legs to create a spider body.

Tip: Practice piping the legs on a plate first to get the hang of it.