Step 1: Prepare the Cupcake Batter

1. Preheat the oven to 160°C (320°F) for a fan-forced oven or 180°C (356°F) for a conventional oven. Line a cupcake tin with cupcake liners.
2. In a large bowl, mix together flour, sugar, cocoa powder (if using), baking powder, baking soda, and salt.
3. In a separate bowl, whisk together eggs, vegetable oil, buttermilk, vanilla extract, and blue food dye until fully combined.
4. Slowly pour the wet ingredients into the dry ingredients, mixing on low speed until just combined. Avoid overmixing.
5. Divide the batter into three bowls. Color each with purple, blue, and pink food gel for a galaxy effect.
6. Gently swirl the batters together before filling the cupcake liners halfway full.

Step 2: Bake & Cool

7. Bake for 30 minutes or until the tops spring back when lightly pressed.
8. Let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

Step 3: Fill with Surprise Sprinkle Center (Optional)

9. Once cooled, core the center of each cupcake using a knife or cupcake corer.
10. Fill with star sprinkles or Pop Rocks and replace the cupcake core.

Step 4: Make the Galaxy Frosting

11. Divide the buttercream frosting into three bowls and color them using purple, blue, and pink food gels.
12. Mix each color thoroughly until smooth.

Step 5: Pipe the Galaxy Swirl Frosting

Plastic Wrap Piping Method

13. Lay a piece of plastic wrap on a flat surface.
14. Pipe stripes of purple, blue, and pink frosting next to each other.
15. Roll the plastic wrap into a log and twist both ends.
16. Snip one end and place it inside a piping bag fitted with a Wilton 6B or 1M piping tip.
17. Pipe a swirl on each cupcake in one smooth motion.

Step 6: Decorate & Serve

18. Sprinkle edible glitter, star sprinkles, and metallic candy pearls over the frosting.
19. Serve immediately or store in an airtight container.