Preparation:

Step 1: Prepare the glasses.
Begin by rimming the milkshake glasses with chocolate sauce. Pour the chocolate sauce onto a small plate, then dip the rim of each glass into the sauce. Immediately dip the chocolate-coated rim into green and purple sanding sugar to create a festive look. Set the glasses aside.

Step 2: Blend the milkshake.
In a blender, combine the vanilla ice cream, whole milk, and vanilla extract. Blend until the mixture is smooth and creamy.

Step 3: Add colors.
Divide the milkshake mixture into three separate bowls. Add a few drops of purple food coloring to one bowl, green food coloring to the second bowl, and orange food coloring to the third bowl. Stir each bowl until the colors are well blended.

Step 4: Layer the milkshake.
Carefully pour the different colored milkshakes into the prepared glasses in layers to create a swirled effect. For best results, use a spoon to control the pouring and keep the layers distinct.

Step 5: Garnish the milkshake.
Top each milkshake with a generous dollop of whipped cream. Add sprinkles, candy eyes, and edible glitter for a magical touch. Drizzle chocolate sauce over the whipped cream and insert a fun-colored straw. For an extra spooky effect, you can add a decorative topper, such as a plastic spider or a mini witch hat.