Petri dish cake

This science experiment themed birthday cake will make all the kids squirm with delight! Great for kid's birthdays or for Halloween parties!

  • 2 hrs preparation
  • Makes 1
  • Print


  • 35 centimetre x 60cm rectangular cake board
  • 85 gram packet mango jelly crystals
  • 3 x 600g packets white mud cakes
Butter cream
  • 250 gram butter
  • 3 cup confectioner's sugar
  • 4 tablespoon milk
  • 4 sour worms
  • 3 blue sprinkle licorice allsorts
  • 11 white tic tacs
  • 1 blue bootlace
  • 1 green bootlace


Petri dish cake
  • 1
    Make jelly following packet directions. Pour jelly into a shallow dish; refrigerate 30 minutes or until jelly is the consistency of unbeaten egg white.
  • 2
    To make butter cream; beat butter until white as possible, gradually beat in half the sifted icing sugar then milk, then remaining icing sugar. Beat until smooth.
  • 3
    Trim icing from cakes. Use a small sharp knife and a tablespoon to scoop out a recess in centre of each cake, about 2cm deep, leaving a 2cm border around edges. Secure cakes on cake board with a little butter cream. Spread butter cream all over cakes
  • 4
    Pour jelly into cakes. Push sour worms into jelly in one of the cakes. Refrigerate all cakes until jelly is set.
  • 5
    Position blue licorice allsorts and Tic Tacs on another cake to resemble microbes.
  • 6
    For remaining cake, cut blue bootlace into small pieces, sprinkle on top of jelly. Cut green bootlace in half; tie a knot in each half and place on top of the jelly for a virus.


We used a heavier-crumbed mud cake as it is more solid and less likely to allow the jelly to leak. Butter cream is firmer than ready-made icing and is less likely to break down into the jelly.

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