Bake Cupcakes: Line a 12-cup muffin pan with cupcake liners. Prepare the cake mix according to the box instructions. Bake and let the cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before frosting.
12 cupcake liners, 1 box chocolate cake mix
Whip Butter: In a large bowl with a mixer, beat the softened butter on medium speed for about 4 minutes until fluffy.
1 cup unsalted butter
Add Flavor: Mix in vanilla extract and salt until blended.
1 teaspoon vanilla extract, ½ teaspoon salt
Sweeten It Up: Turn the mixer to low and slowly add powdered sugar, one cup at a time, until fully mixed in.
4 cups powdered sugar
Smooth It Out: Add the milk and beat just until incorporated. Scrape down the sides of the bowl, then mix on medium speed for 2 minutes until the frosting is smooth and creamy.
2 tablespoons whole milk
Divide and Color: Split the frosting evenly into three bowls. Add neon gel food coloring to each bowl—one green, one orange, and one purple.
Gel food coloring
Pipe Swirls: Spoon each colored frosting into separate piping bags fitted with a Wilton 1M tip. Pipe swirls on top of the cooled cupcakes by starting at the edge and circling inward until you reach the center. Repeat for all 12 cupcakes.
Sprinkle Magic: Add Halloween sprinkles on top. Serve immediately or store in an airtight container at room temperature for up to 3 days.
Halloween sprinkles