Steps
1. Preheat oven to 175°C (350°F). Grease and line three 10cm round cake pans.
2. In a bowl, whisk egg and sugar until pale and fluffy. Add melted butter and vanilla extract; mix well.
3. Sift flour and baking powder into the wet mixture and gently fold until combined.
4. Divide batter evenly into three pans. Bake for 12-15 minutes or until a toothpick comes out clean. Cool completely.
5. Whip 50g heavy cream with 10g powdered sugar until soft peaks form for plain cream.
6. Whip 40g heavy cream and 10g powdered sugar until soft peaks form, then fold in peanut butter gently for peanut butter cream.
7. For buttercream: Beat softened butter until creamy. Gradually add powdered sugar and milk until smooth. Add blue food coloring and mix until even.
8. Assemble cake: Place first sponge layer on plate, spread plain cream evenly.
9. Place second layer on top, spread peanut butter cream.
10. Add third layer.
11. Frost entire cake with blue buttercream smoothly.
12. Sprinkle crushed cookies around the base and some on top to simulate sand.
13. Decorate with edible Hawaiian flowers, the edible surfboard, and beach-themed decorations.
14. Chill for 30 minutes before serving to set frosting.