Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners. Mix your preferred cupcake batter until well combined. Pour into liners, filling each two-thirds full, and bake for 18–20 minutes or until a toothpick comes out clean. Allow to cool for 5 minutes before transferring to a wire rack.

In a mixing bowl, beat the unsalted butter until creamy. Gradually add sifted powdered sugar and milk, mixing until smooth and fluffy for about 3–5 minutes. Set aside some frosting for tinting.

Divide the remaining frosting into bowls according to the number of colors. Tint with gel food coloring for your desired design.

Decorate cooled cupcakes using piped frosting for monsters and jack-o'-lanterns.

Spread white frosting on spider-design cupcakes, pipe black frosting for web patterns, and place mini Oreo cookies and candy eyeballs to finish.

If preparing ahead, refrigerate for 30 minutes to set the frosting.